If you get the same exact RAM, for the most part you'll be fine. The extra power draw isn't major. I had 2 sets of 2x2GB G.Skill and OCZ and didn't have any problems. The only reason I got rid of the G.Skill set is because it died, I RMA'd it, and decided to pass them off towards my mother-in-law's new build.
And yes, by the time we even get CLOSE to needing more than 8GB of RAM, you won't be wanting that RAM at today's speeds. (1600/2200MHz)
Cables, it still amazes me when I see E8400s alive at 4.0GHz. I know it's EASILY accomplished on that chip, but it still just amazes me. I had one at 4.2GHz stable with probably less voltage than my Q6600 has now. Great CPU. I'd say the 2500k/2600k are the quad core E8400s. Edited by Stealth Pyros - 3/24/11 at 1:25pm