crashman (the only poster in this thread with any seniority over myself), is right. You need to consider other options realistically.
If you have a $750 budget, we don't know if you need a monitor.. and your going to need a case, PSU, everything then you better stick with the best deal available, price performance wise.
I'd suggest a $80 Athlon 2500+ Barton core, a loaded Nforce 2 motherboard ($120) including Nvidia SoundStorm and built in NIC, and built in GF4MX. Then get your ram, which I'd recommend two 512mb sticks of ddr400 ($200 for both from crucial), setup in dualddr.
You need a HD, one similar to mine is very good in price/performance ($100), a 8MB cache model get either western digital or maxtor.
See we're at $500 and we're not even done yet..
and believe me this system is NOT anything to spit on and its goign to be a very good performer. Intel 2.8 has created many new fanboys but you dont get the advantage of using a Nforce motherboard (hence saving a TON) and you also pay about double the price for a CPU alone. The 2.8 is good but your going to sacrifice in other areas to go that route with your budget. And the 2500+ isnt that far behind in my opinion to cry over, especially for the price. Its the cheapest Barton core with the extra cache.
Ok back to business, you are at $500, you need a case and HS/fan, a good Antec case is about $100 and a good HS is about $30.
We have $120 left and unfortunately we're stuck with the GF4MX, which will get you by until you can get ahold of a 9800 Pro or FX5900. But you gotta have a monitor and mouse/keyboard and a CD drive. You can get a good lite on, 17" monitor for that if you shop around.
If you dont need a monitor, I'd suggest putting all that money into saving for a good video card, if it was me, I would use the MX until I could afford something worthwhile, a 5900 preferably or a 9800 pro. Skip the middle of the road cards. I was considering a 9600pro/5600 for myself but your better off just saving the extra $100.. its not that much money and the performance difference is quite noticable.
Athlon 1700+, Epox 8RDA (NForce2), Maxtor Diamondmax Plus 9 80GB 8MB cache, 2x256mb Crucial PC2100 in Dual DDR, Geforce 3, Audigy, Z560s, MX500