Performance under mixed workloads, duals vs quads

I'm scoping out components for a new workstation, so I've looked at the benchmarks on this site pretty closely. I don't care about gaming or video. But at any given time, I'm normally running the following under Vista 32b: a development environment (including test instances of apache/tomcat and mysql), an audio playback app, an MPEG codec, email, and > 10 or so browser tabs open — all memory hungry stuff, but except for the development and web environments, not much in the way of multi-threaded apps, but a lot of apps. So, assuming I'm not ready to go with an i7 solution, I would think that I'd be able to make use of all 4 cores on a quad LGA 775 chip.

However, I've benchmarked enough UNIX servers in my day to know that just going to four cores on the same socket architecture won't help me if there's not enough memory bandwidth to keep the beast fed. The way I've always checked that on a UNIX box was to benchmark an entire workload simultaneously — time a mix of apps with different runtime characteristics through to completion.

Has anyone on this forum done such a test for the Quad duos vs. the Dual chips? I wouldn't mind seeing the same results for the i7's, too, since if the answer comes back grim, I might have to bite the bullet and go that way.

Thanks!

-- Ed