If you want lossless reproduction it would appear that the uncompressed AIFF file format is best. In What Format Should I Rip My Music? | Computer Audiophile
However, you also need to consider how much storage space you have as 800 CDs will take up a fair bit of disk space.
Personally, I've tried MP3, MP4 and WMA and didn't notice any discernible loss in quality - I suppose a lot depends on how good your hearing is.
Don't forget that MP3s are free of Digital Rights Management and can be played on all types of disc player.