The Epox nforce 3 250GB is a pretty good socket 754 board. You don't need pci-e right now, so 754 is a pretty good choice. Your processor is fine too. Get 6600GT AGP btw. A socket 754 based computer can last you 3-4 years, and when thats done, you can buy a new comp. Technology is always changing, so you don't know when your so called futureproof setup isn't so futureproof anymore.
Also, if your into overclocking, you can run the ram divider to 3:2 on a 2800 sempron and get decent results. It will save you 70 dollars, and you can get a 6800GT AGP with the money instead of a 6600GT. If you don't want to overclock, forget what I just said.