No effect except for quality. Prob wont be too noticable either except for the odd bit of treble. Volume differences or noises will be due to the original recording not the bit rate. Just account for different volumes during mixing, easy enough
Hmm pcdj is one of the faves as is traktor 2. Both require you to either buy them or crack them. However, some people have found that traktor realises its cracked and tells you not to use the program again otherwise it will delete all your mp3s! Its probably just a dodgy crack though. I would probably just stick with pcdj though, its easy to use and has everything you need to get started.
Pcdj fx is the newest version which has a sampler, master pitch controls etc but for simplicity i would use pcdj red. Its just like a half decent cd player, you can set loop points/cues etc as well as doing motor downs/brakes. You should be able to get a copy off soulseek for "trial" purposes of course!
With most djing apps you are going to need either an sb live based card or 2 sound cards. One for monitoring and one for output.
I originally used VTT (Virtual TurnTables) for 3 years. Since switching from a tower to a laptop 18 months ago I wasn't able to use VTT (wouldn't work properly in XP). So, I switched to PCDJ with DMC-01 controller, I now use PCDJ FX exclusively (with the same controller). These are ligit and paid for of course....................although I have got .............
PCDJ FX does NOT have sampling, yet! It does however have the best Master Tempo on the market as well as looping, effects, loop editing and a mixer with eq kills. There is a new version due anytime in the next coupla weeks, this is re-written to accept module plugins. The first module plugin is a Karaoke plugin to be released on 1st September. A video plugin will follow.