I'm not familiar with that Swiftech kit, but assuming you have an adapter for Socket 775 you should be okay as long as no capacitors are in the way of the water block.
Whether the new 45nm chips are worth it remains to be seen, all I've seen is ES chips clocking like mad, but you never know if those are cherry-picked to bring on the hype for what I feel is just a die-shrunk Core2 chip with SSE4.
There are X38 boards with DDR2 RAM slots, you can seperate them on Newegg when you browse on there. The Asus P5E and Abit IX38 I mentioned earlier are both DDR2-slot boards.
I wouldn't trust Newegg reviews too much, most of the people on there don't really know what they're talking about. I'd trust a senior OCF-er over dozens of Newegg reviewers.
Is the X38 better than the P35? Yes and no. The main distinguishing feature with the X38 is full x16 PCI lanes. Here is a link with a really simple explanation:
http://www.bit-tech.net/hardware/2007/10/12/crossfire_comparison_intel_x38_versus_p35/2
If you're going to go with two video cards you might want to consider an nVidia 680i or 780i motherboard. They come in much cheaper than the 'premium' X38 boards and offer pretty much the same performance, in my opinion.
Going with an nVidia board you don't have to pay $240+ for an X38 board to get "full" SLI capabiltiy.
Only reason I might avoid an nVidia board is the P35's can overclock to 500+FSB with less effort than the nVidia, but that only comes into play if you have a low-multi chip, but with the Q6600 (x9) it shouldn't be a problem since you'll be hitting 3.6ghz at just 400FSB, which should be a cakewalk with whichever chipset you decide to choose.