If all you are looking for is a lot more speed cheap, get a 100MHz bus celeron 800, put it on a slotket FC-PGA to Slot-1 adapter with voltage adjustment, put it in your existing motherboard, and make your computer twice as fast for about $75. Need more memory too? Spend another $20-$30 and get 256MB of PC100 or PC133 SDRAM (get the PC133 since it is the same price) and put it in there with the new celery stick. Make sure not to get the high density stuff, as it won't work in your motherboard. As far as the video card goes, get a cheap Radeon LE. I have seen them go for as cheap as $60 on the hot deals board. If you do a lot of heavy duty photo or video editing, etc., and NEED the extra 128k of L2 cache that the PIII has over the Celeron (that, and dual processor capability is the only significant difference between a coppermine celeron and PIII), spend an extra $50 and get the PIII instead. You might need to flash the bios on your motherboard to make all of this work.
There you go. You now have an 800MHz (100MHz bus) computer, with 256MB SDRAM (plus whatever you already had), and a video card that will more than keep up with your system for well under $200 shipped.
OR, you could spend a grand and build a really great AMD system. Personally, I would spend the $150 now, and wait for nforce. It will make a great second PC when you build the real one.
Nack