Price is not an issue ... I already own the quad, and a friend wants to swap his e8400 straight up for it. The retail prices are pretty even, both between about $150 to $180.
The mobo supports the full line, all the duos and all the quads ... it's really a beaut of a mainboard: http://www.msi.com/uploads/prod_4ef3ead843de4d140d00c5f507d9517f.jpg
I guess the software I'll be using is the key factor ... I hear you that the audio recording would be better with the quad. So what is better wit the Duo? What advantages does the faster clock speed give me? It's 25% faster, and there's 50% more cache.
And thanks for the welcome, and the responses. I posted the same question in the Intel forums 3 days ago, and still nothing.