Hoster 3.0 was just to get you playing your MP3+G songs. The whipped cream comes later.
Hoster 3.1 coming first quarter next year will allow importing MP3+G and ZIP songs into the Songs Database, without changing the format to KMA. You'll have to do something to tell Hoster what the Brand, DiscID, Songname and Artist Name are, and have Hoster assign a BookID to it. Otherwise you can't find it by those items in the BookID, Brand/DiscID and Search "Add Track" options.
These songs will then also appear in your Hoster Song Book.
This should end the speculation.
It is generally accepted in engineering circles that when a file is compressed and decompressed, then compressed with another compression means, the loss is only from the worst of the two, there is no "compounding". Thus, your MP3 songs will sound the same after decompressing and recompressing with WMA. WMA is accepted as the superior quality.