I didn't do FLAC but did WMA-Lossless. Lossless does sound better than mp3.
Used Windows Media Player (set up to auto-rip, making it relatively easy to do)
Originally ripped 50 CD's, first in MP3 (max sample rate)
Re-ripped the same 50 CD's in WMA-Lossless (after I bought the car) - Size - about 20gb
Put MP3s on one USB drive, WMA-L on another USB drive
Both plugged into glove box USB slots.
Easy to compare by switching between the two.
Have the HK system.
That all said, even though the lossless format sounds better and that's my default pick, I also have older mp3 files and listen to them without disappointment, but if you have a choice, rip lossless. If you don't know what a "CD" is....never mind.