Nothing about that computer screams "Buy me".
Best Buy is typically overpriced for gaming machines. I'd even recommend TigerDirect/CompUSA over Best Buy for a gaming rig. Even Dell PCs can be easily upgraded to be more "gamer-friendly".
Processor - The 4th Gen Core i7 is a good choice - can't offer much advice on that. Processors are a bit more beastly to swap out (primarily due to motherboard/processor compatibility), so definitely target systems with the processor you want. Everything else can be upgraded after the purchase.
Video card - I have a Radeon 4890 - it is sufficient to play GW2 and BF2, but I haven't tried it on more recent FPS games (not my style). Use this site to compare video card specs and "prices":
http://www.videocardbenchmark.net/high_end_gpus.html
My 4890 ranks around 1500, where the GT 640 in the BestBuy system rates only around 1285 - so there will be a small difference between the two.
According to that site, you can get a GTX 7850 (rank around 3700) for around $130 (probably cheaper, if you look hard enough). It makes the top 30 of the list, and is one of the best bang-for-the-buck cards I've seen. Video cards are easy-peasy to install, so don't let that scare you off from upgrading.
Memory - 16GB is certainly admirable. You can buy 16GB of memory (4x4GB) for around $100 if you look around. Manufacturers like to overcharge for that kind of thing, so be mindful that memory upgrades can be much cheaper (and very easy to install) than trying to get a system with exactly how much you want to end up with.
Two words of advice:
1. Shop around. Visit sites like FatWallet and SlickDeals to find killer deals on systems. Computers are hot items that often pop up, and finding systems at 50% off list price is rather common.
2. Black Friday is JUST around the corner - and things go on sale for DEEP DISCOUNTS. If you're patient, you can very easily capitalize on one of these sales. Remember, prices continuously drop, so if you don't get anything that weekend, the prices will likely still be better than they are right now, especially as the Christmas season continues on.
A quick search on Slickdeals turned this one up:
http://slickdeals.net/f/6378654-ref...ac-or-12gb-2tb-hd7770-645-ac-free-ship-newegg
If you're OK with a refurb, this Dell has the same (or similar) processor, a better graphics card (one you wouldn't want to immediately upgrade, anyways), 12GB of memory, same 2TB hDD and is over $300 cheaper at $645. But comments on this post even hint that there were better deals offering similar systems with 16GB memory for $500 - you just need to keep you eyes open for these sales to pick up.
Just my two cents - I've found that when buying computers, fortune favors the patient and alert.