help building a new system on a budget...

i want to move on from my "16-year-old-this-is-supposed-to-be-good-and-it's-cheap" system and need some help. i'm looking to go tube -- do i need both preamp and amp, or just an amp? i also want an older pair of floor-standing speakers. my budget is limited (around 600 or 700 would be nice). i basically want something that sounds a little warmer and more real than what i have now, and that will be equally at home w/ records and cd's playing rock, jazz and classical. my room is small (roughly 18 x 12) and has hard wood floors w/ an area rug (if this makes any difference). if you have any suggestions, please shout 'em out. thanks.