Advice for plunge into digital!

Hi folks :)

After years of playing with CDJs and DJMs, and sick of burning CDs .. im on the verge of moving across into digital and playing with traktor.

ive begun the move by getting an old lenovo x61 to mess around on ... cost me £81! but is a core 2 duo, 2ghz, 4gb ram, windows XP so should be enough to get my feet wet.

my conundrum is what to actually buy next/what i need. currently, i record into a desktop PC which has an m-audio 24/96 PCI soundcard, ideally id want to replace this with a USB soundcard but damn they are expensive? im only interested in using 2/3 channels, am i right in thinking the audio 4 soundcard will do the job for me with the setup i have? (2x CDJ 1000 and a DJM 700)

i would ideally like to keep the DJM 700 and CDJ 1000s purely because they are still in most bars/clubs so i can keep the familiarity there. i know that its possible to map the DJM 700 with traktor, has anyone done this and is it any good? im wondering whether i could take a laptop with me to a place with these installed and then use the DJM 700 to mix with. is that possible?

i also seen some people use a kontrol x1 with a DJM 700, how does all that work?
as you can probably tell im a bit clueless as to what path to go down, too many options!

cheers.