Well, turns out the PII 955 Deneb AM3 is cheaper than a Wolfdale E8400. In this case, I would stick with this quad-core.
As far as a motherboard, I would grab this:
http://www.newegg.com/Product/Product.aspx?Item=N82E16813138130
I have the stepped down version of that (TA770+ A2) and it OC's pretty well. If you have more money to dish out, try this one:
http://www.newegg.com/Product/Product.aspx?Item=N82E16813131366
As far as heatsink, I'd grab a cheap Xigmatek to begin with. Unless you're going to be really hardcore, this should be an excellent buy at a cheap price:
http://www.newegg.com/Product/Produ..._re=xigmatek_hdt-s1283-_-35-233-003-_-Product
NOTE: I'm pretty sure AM2/AM2+ heatsinks fit right onto AM3 sockets. I may be mistaken, I want someone to confirm this for me.
Lastly, you can post specific questions about OC on our OC/Modding forum. I will be writing a brief guide soon.
