I think it all depends. If you're moving between places alot and constantly need a computer with lots of power than a desktop replacement makes perfect sense. But, if you just leave it at home on the desk and never move it then it's kinda pointless. That's why I kinda wished I had gotten a...
Hm really loud ticking usually somethings wrong you might want to try and run a program that can detect the HDD's HD smart log (or w/e it's called, I know it's HD smart).
Um, hmm any other like programs to OC graphics? Like I use ATI tray tools (I think it's been a while) and I don't think it really cares but I'm using an ATI card. I would try programs you would use for a desktop graphics card before trying obscure programs.
I'd say go with the 800 mhz ram. It's 15 bucks and then the ram will probably be able to overclock higher and if you don't overclock it'll at least be faster.
How would you get 8 signals per clock cycle? Like DDR runs at the max and min I believe, QDR would be max, min + x intercepts? And ODR would be well i have no clue...
I think HDD's will stick around for a good while. I mean you don't need uber fast read times on movies and photos and such. So I wouldn't be surprised to have something like an 80-120 gb SSD for the OS and programs and then a traditional HDD for storing all your media and documents.
You have to play with pll's...although as far as I know clockgen hasn't really worked with core 2's. And btw I can overclock my gfx card just fine by turning the fans up to high....maybe if you're running a mobile pentium 4 then the stock cooling will be overload, but modern core 2's run fairly...