I don't know what the obsession is with faster processors in the Mac Pro. Sure, 5 or 6 seconds less in a 3 minute processing task would add up eventually, but the real drawbacks to Mac Pros are:
1. Lagging video card tech
2. Expensive and/or useless RAID options (Apple's is too expensive, 3rd parties are scary due to their possible lack of future driver support and lack of SMART/boot capability)
3. Overpriced, overly-hot, sluggish RAM
4. Lack of Blu Ray (who cares about support, a burner would be nice)
To me, any one of those problems being solved is going to be worth more than a few more megaflops. I mean how fast is the MP nowadays? 8 Core 3ghz? HOLY $#@%!!
And yes, I know you all are going to "blame the 3rd parties" and Intel for problems 1-3, but that's beside the point. I'm just saying: probably more important than a slightly faster proc are these things.