What am i missing out on?

If you have a AM2+ motherboard and there is a updated BIOS for that brand it would be far cheaper and more economical as an upgrade to go for a AM2+ Phenom II rather that build a AM3 Phenom II system from scratch.
The AM3 systems will probably be a little faster perhaps by just a few percent than the AM2+ ones using the Phenom II.
Would you spend $800 to $1,000 on a new AM3 system when instead you can just plop down say $250 to $300 on a AM2+ 3 Ghz Phenom 2 940 that's just a few percent slower than the AM3 945 one and use it in your current board perhaps? For perhaps $200 more you could go Intel's Core i7 route which is more powerful than a AM3 3.0 Ghz Phenom II 945(These will probably be available in April or May 2009).
The AM2+ versions of the Phenom II are the upcoming faster replacement for the B2 and B3 stepping Phenoms.It will be released I think in Jan and perhaps available retail in Feb 2009.

Thanks guys. Friend of mine has a 9950 for 150 dollars brand new and i think i'm going to take it. Thankfully my motherboard is an AM2+ so i can just plop it right in.