the best performance:money is always the cheapest cpu, if you factor in overclocking
🙂 a s754 2800+ i played with recently has no problems running 2.4ghz at stock volts, and above 2.5ghz at the tiniest overvolt. with stock cooling too! they aren't all equally good, but the chance that it'll clock up is pretty good.
the next best buy is a chip with 1mb l2 cache - i thought the 3500+ was the cheapest of those, and still not anywhere cheap enough to be worth it.
but hey! newegg has some "DTR" athlon64 clawhammer 1mb l2 chips at ratings 3000+, 3400+ etc, like this one:
http://www.newegg.com/Product/Product.asp?Item=N82E16819103470
the picture of it looks like an athlonxp though, so i dont know how legit that is, if someone can shed some light on it i would be grateful.
if you can find a 1mb l2 chip cheaply, it could be worth it (you can't gain more cache by overclocking, unlike raw clockspeed)
i don't see a point going for anything faster, as you can usually achieve those speeds with the cheaper models anyway.
i think its not a question of IF, but rather WHEN will you move to socket 939, pci-express, dualcore cpu (AMD will be launching their sub-$400 dualcore soon) with atleast a gig of ram, preferably two. that would be more a completely new system than an upgrade, and will be quite expencive, so i wouldn't be wasting cash on a s754 3700+ if i were you. better save up for a couple months, wait for the cheaper dualcores, new vidcards etc, and when you think the time has come sell your current rig and buy one that will probably last you some 5-10 years.