Mouseman,
You mention playing these files on your, "DJ computer". Are you playing these files in a club, or at home? If it is a noisy club you could posibly get away with alot of the lower bitrate files. If it is at home, where there is a definite difference in acoustics, you should probably stick to some the higher quality formats mentioned above.
I guess location should be a consideration as to what type of format you choose. Anyone can say they hear a difference where it is quiet and you are really concentrating on the music. Don't think that would be the same case after a couple of cocktails at the local pub. People talking, room acoustic footprints, etc., would change the way any format sounds. And posibly hide flaws in lower bitrate files. Good test to try, move the furniture around in your listening room at home and see what a diffrence that makes. Sound gets bounced in different directions now and completely changes the way your music gets to your ears.
Recently, I changed the location of my speakers in the living room. Basically moved them off the floor about 16 inches. WOW!! Had to really turn the bass down. The passive ports, located at the bottom of the speakers, no longer lost their punch due to sound crossing over the carpet. Best guess anyway. Sub-woofer had to be re-adjusted also.
So, we should ask, where and how does your music gets played?