In the UK, the fastest new processor is a Sempron 3000... I don't know where you're from; or if you're willing to go the used route... but it's what I had to go for.
This was the problem I had about a fortnight ago; my 3200+ Clawhammer just stopped working. I've got the Sempron in my Socket 754 board now, but it's not a good experience.
I'm going to go cheapo C2D - E2140\ASRock AGP\CheapDDR2... the ASRock board will even accept normal DDR. Socket 754 had such a short mainstream lifespan - about 6 months - and so we're screwed, really. There's very few of us S754 users around, and the lack of decent product reflects that.
Sorry mate; but if you're looking for a decent upgrade, forget socket 754.
Damn you AMD!!!