HDD prices aren't dropping, SSD prices have been falling rapidly since their release. HDD prices have actually increased due to real world problems in Taiwan over the last year or two. Looking at your gfx card I'd compare it to the 6990 just based on available numbers. Just based on what I can scrounge up the 7870 is about 50-70% of what a stock 6990 would be and that card only has 2gb of vram which is what the 6970's were running.

You'll start to see vram maxing out when you try to crank up settings like AA MSAA and basic graphic quality. The processor typically falls under the highest load when running extra things (shadows, smoke, particle effects). I might be talking out of my ass here but I've played BF3, Metro2033, and a few other high res games and this is just what I've noticed and double checked on OC forums. Keep in mind that the new series of AMD cards is supposed to release around christmas, and like I've said before, I can let you borrow (til the AMD release) a card or sell you a decent one for cheap (cus we friends and I'm fuckin cool like that).