well, if you are using games and apps that you KNOW are thoroughly multithreaded then you will be able to actually use your X2. but its more expensive and less of a performer than the 3700+ if not. My take on the multi core procs is that as the technology is used by more software, the prices on them will have relaxed significantly. Just look at intel's 3 and 4 core processors in the works!!! paying 100 bucks more now for a multicore processor that will be very outdated very soon by a cheaper, more 'necessary' one in the future isn't my cup of tea. But, of course, maybe you are using more suitable apps than me!!!!
same with the SLi deluxe board. It's fine if you don't need the heat pipe, "hi-def" sound , or other options on the premium.
My CNPS9500 cools like a champ (maybe because of my case's air flow or stock voltage though!) and my max load temp never hits 39C in a 72F room. I would imagine that with good case air-flow, 2.6 MIGHT be possible with safe temps on a 3800x2.
I know as much as the next guy how easy it is to want more for just a little more money. But that "little more money" adds up fast as hell over a few components!!!
I really wish I had only gotten the 1GB RAM, etc. Oh, well... Hopefully my comment is helpful!!!
congrats on your awesome new gear BTW!