I've wanted to post in this thread since it started, because I find myself in the exact same situation, choosing between these two processors. When it first started last week, the general consensus in this thread at the time was to go with the Q6600, while I'd been leaning towards the E6850. I felt like I shouldn't bother posting what I thought because with so many people saying to go with the Q6600, I was afraid that I'd be, I dunno, generally verbally rebuffed, and with the discussion all but seemingly finished anyway, I thought 'why bother'.
Meanwhile, I looked at my financial situation, and how much I'd have to spend, and it seems I'll have to wait 2-3 months anyway. Nvidia's next card will be out by then, which I also want to get, and the newest Penryn cores will be as well, and I can re-evaluate the situation.
Had I built the PC now, I would have went with the E6850. I want raw horsepower over all else, and Quad cores aren't there just yet. The Quad core equivalent of the E6850 with a 1333FSB and a 3Ghz clock speed is the QX6850, at ~$1350
http://www.newegg.com/Product/Product.aspx?Item=N82E16819115026, compared to ~$320 for the E6850 on Newegg
http://www.newegg.com/Product/Product.aspx?Item=N82E16819115028. I can wait till the Penryn CPUs are out to see what changes, and even if nothing worthwhile does, a least prices will drop. Also, its been said here before, it'll be very easy to upgrade later on anyway.
I just hope this doesn't come back to bite me in the ass in the end. When I bought this PC in Sept 2005 (Dell Dimension 9100, they changed the name to XPS400 soon after I got it), the stock configuration was a dual core P4 @ 2.8Ghz. I wanted raw horsepower, so I went with a single core 3.0Ghz instead. I realize now I should have went with a Dual core 3.2Ghz.
Anyway Good Luck to you Gary. Try and post how it all ends up for you, I'll be doing the same when I build my rig later on this year.