Well, likely your common driver set would be ASIO these days unless something else is gonna supercede that.
In theory that allows a lot of stuff to work with each other, and the good part is that generally the hardware mfg has to write the drivers for their particular box- and (hopefully....) update them as new things like Vista come along. Just look at the big variety of F/wire, USB2, and PCI and other interfaces out there today. Most talk to the software via ASIO drivers though lower end stuff tends to run with "Windows Sound" only. Some can handle both.
One place to get familiar with what's around would be:
www.americanmusical.com
or same guy's other site which is:
www.zzounds.com
They have links to various mfgs there too usually on the product pages. This is same guy who also used to have Victors that I tried years ago to put Dave together with. They sold Victors to Guitar Center but he kept the 2 internet businesses which are very large, he's like the 3rd or 4th largest seller of most things he carries.
The price point for most of the more comprehensive programs around seems to fall anywhere from say $400 up (software only) so there is a lot of room depending on what it does and how you can sell folks on the perception it will do that better than other products. Bundled hardware/software solutions go for more of course, such as Digi -- though after they bought M-Audio and other companies, they now seem to offer something at just about any price point. Their web site has an overview. The logic of that approach for a marketer is obvious, though only a big player with lotsa $ can do that now I think. It's the "oh you want THAT? Sure, just send this much money(and maybe your old unit)" approach.
It's def become a list/street price situation too. Resellers are very big in this stuff, the larger ones include the 2 above plus folks like Sweetwater, Full Compass, BSW, others. And.. of course.. the 20 ton gorilla-- Guitar Center and its various divisions (at the high end, GC Pro). Pricing follows the MI (musical instrument) model often, and buyers expect big discounts off inflated list prices, and resellers expect good margins too. They won't feature (often won't stock either!) anything w/o that -- and they want all sorts of other sales incentives like co-op ad money too. It's not unlike supermarkets who get paid by manufacturers for their shelf space, product placement and promotion - or the car sales business!
Only the very high end still works a little differently. A few companies like Apogee, Empirical Labs, Massenburg, John La Grou and others can counter the "box-sell" model but even there I think they have to do same types of things at times. John would obviously know more about that. But in that world, it's always hardware or hardware/software-- it's what makes 'em different. And they usually have networks of reps who add a layer of cost to the equation, though often can provide some value if they are good.
So to be software only and to be able to run on a variety of platforms, you would likely have to fall into the lower price point area - again maybe around $400 street price. And upgrades to signif new versions for much less.
With Audition, I think the Adobe Direct price for the full version is $349 plus shipping, but Amazon and others sell it for a bit less with free shipping. The upgrade price (for users of ANY previous version) is $99. They also make a more basic product called Sound Booth, which is something completely different, and that sells direct for $199, again avail through many resellers.
Most of course also do the "educational software" thing too - that's become pretty established now.
Another thing to look at for what you mention about de-noise might be to develop it as a plug in or something that can run in other hosts. Direct X is still used, but seems not the more preferred format these days, it's moved more to VST, VSTi for "virtual instruments" and something called AU (audio unit) that I have not messed with. A few companies go a different road, like Universal Audio with their proprietary format that will only run on their own DSP boards, which they make as PCI and PCIe, also in some outboard configurations.
www.uaudio.com. It will run however on many hosts, and I think currently under VST only, though older versions also ran Direct X.
It even runs on some hosts they don't officially support, like earlier versions of Adobe Audition (I've run it under version 1.5 which they don't support)
But they sell their stuff through the same MI channel discussed above, in a variety of bundles (hardware/software). The difference there is once you are in their world, you will most likely deal with them direct for upgrades and additional software purchases. Every new software upgrade (all free) gives you one-time 14 day demos of new plug ins they develop-which you can then buy if you like 'em. They also offer incentives to returning customers-- once registered as an owner, you get many offers for deals and promotions run directly by them. I just installed a new version that's Vista compliant (but on XP) and in my account went a $50 off your next purchase voucher. It just runs the plugs I'm authorized for unless I choose to buy (or demo) more.
One thing that is expected (or at least hoped for) as you move up the price point ladder is comprehensive support. Some can be pay for support, but companies like Univ. Audio offer a lot of support for free. Adobe offers installation support only for free, and a variety of paid support options.
Waves offers free support and upgrades for 1 year, after that you must buy their update plan which is priced by what you have, often about $200 a year or so. They won't much talk to you unless you're covered under the update plan. And though they've become better on Windows things, they still come at things from more the Mac world, like Digi does as well. And they use the Ilok key, which can be a whole other can of worms- you have to get its drivers from Ilok (Pace), but Waves doesn't follow the full Ilok authorizing scheme, they use their own but on that key.
Izotope offers mostly free support, and is very friendly about authorizations for their stuff- I suppose unless you abuse the privilege!
You can authorize any of their products to either a hard drive or a USB flash drive which you can then use on any system as its "dongle". Upgrades so far have been free. (
www.izotope.com) I've used their Ozone quite a lot, it seems well-integrated, but it definitely uses a lot of CPU resources. Also their stuff will run as demo unauthorized for a while, after that it will still run with no key inserted but will add some noise every so often and gently remind you to authorize it. Waves won't run at all without its authorizer inserted, and might crash your host too.
I hope you will consider redevelopment, I for one would be interested. I'd echo a lot of Jim's thoughts however as being necessities for any editing and mixing plaform these days. Hope all this is helpful to you.
Rich