It's a sort of off-topic here, but you shouldn't give that app too much credit.
Soundtaxi (and Tunebite and a ton of other apps) is just a glorified sound recorder, so you lose quality (which is often not that great already) due to reencoding. There are lossless solutions, which only decrypt but do not recompress your files:
1)
FairUse4WM for WMA files.
2)
QTFairUse6 for iTunes music.