Hi, I'm Robert from Michigan...
I'm assuming your asking because you no long have the CDs?
When you use DBPowerAmp. If you want the best quality, do not use MP3. MP3 (256, 320) constant stereo bitrate is really good, and I don't think you'll find many truly honest people that can tell the difference between that format and the CD-Audio. But If you want to be sure, and I do this myself: I would recommend M4A (Apple-Lossless), or 'Flac'. It depends on what player you regularly play them with. DBPowerAmp can convert to these 'LossLess' formats.
Or Did you use less than 256bitrate? Old MP3 standards were like 128? Free Pandora broadcasts at like 96.
But... Here's the problem. You've already created the LOSS. Don't let anybody tell you that can restore, what isn't there.
The best we can do is add or edit something... Like 'Volume', "Normalization', 'Bass', 'Treble', do some fancy sound editing..... which should be more expensive