Actually, for $2000 you could get yourself a newer EX500 or GS500. Last year, I picked up my '99 EX500 for $1800 which was in decent shape and ran nicely. If you think you can handle a 600, you should look into the older F2's or early F3's. Katana 600's are ok, but a bit on the heavy side.

There are deals to be had, you just may have to travel to get them. Figure out the maximum distance you will travel for a bike, and start checking craigslist, this site(most bikes are a bit overpriced), cycleforums.com, and platform specific sites such as cbrworld.net.

Make sure you don't blow your entire budget on the bike alone. You'll probably want to save up 500-750 for some good gear. Also, make sure you check out skr00z's sticky on buying a used bike.