Trefor Patten said:
AIFF and FLAC are the same quality. AIFF is just Apple's PCM/WAV format. FLAC is losslessly compressed PCM. When played back they sound exactly the same.
Weeeelll, they should sound the same. In my experience AIFF has a slight edge in quality, though this may be system dependent. If space is available I would rip to AIFF (or WAV) as this is the 'cleanest' format for re-conversation at a later date if necessary. All my music is archived in AIFF and some copied to MP3/FLAC/AAC/Ogg Vorbis for playing on phones, ipods etc.
They do sound exactly the same, unless there is a problem with your hardware. The FLAC is converted into exactly the same format , and more importantly, exactly the same bit-for-bit file before playback. The processing power for conversion of FLAC is negligible. It works perfectly on many portable players, so for a computer, or a NAS drive it's next to irrelevant.
FLAC or any other lossless format is a much better format for storage, is better for metadata, and just as easy to convert, especially as the OP has dbPoweramp which makes life very easy.
For the moment also, FLAC is the de facto standard for lossless downloads.