I use a Rane TTM-57 Mixer with Serato and effects built in, obvously scratchLive, and a 2.4 ghz white macbook 2 gb of ram, 160 gb HDD... This is the only time I've ever incorperated my computer with any of my DJ and recording, and I couldn't be happier with the results. You still can't take away my standalone multitrackers, and samplers though... NEVER!!!!! If you're really djing with turntables serato is the way to go, you don't have to get the 57, but if you're shopping for a mixer you might as well get it now, as you'll end up with a rane mixer anyway. Anyone feel free to pm me if you have any questions about this kind of stuff, I love talking about it!
By the way I use technics 1200 MKII with shure M44-7 needles