Sniper is right on the ball, I would just get the 4870X2 right off the ball, not much point sticking with the 9800GT. I'd also recommend going with the WD 640 Black Edition drive in your initial build. Other than that your initial build looks EXCELLENT.
As to the "future/dream build" I'd first of all drop the plan to go to the Rampage II Extreme, you do not need it, most of its features are suited toward hardcore overclockers and outside that segment there are little to no features/performance improvements over the P6T in your initial build.
I'd also drop the plan to go with OCZ SSD's, with the exception of uber expensive microns and the not expensive but hard to find Intel SSD's, most SSD suck. This will change in the future, but for now they are generally not worth it. That said, if you want to go with the blazing speed of an SSD, go for an Intel one, they seem to be the only affordable ones with any decent performance.
Now to your want for a moderate overclock, grab a TRUE(Thermalright Ultra 120 Extreme) for around $70-80, slap it on the i720, and I guarantee you'll get at least 3.6GHz out of that puppy. When it comes down to it you do not need to watercool it. That being said watercooling is always fun, and usually can help improve your OC'ing performance, weither you'll be able to fit it into that case thou is a whole other issue, I'd stick with air cooling for now if your new to the OC game.
Hopefully we've answered many of your questions, if not, feel free to ask! As for the specifics of OC'ing, comeback to use when you have your system we'll be more than happy to help.