AMD's Price/Performance ratios
Once upon a time, maybe. Today, the differences are negligible, or even in Intel's favour for quite a few actual applications (in particular games) as opposed to synthetic benchmarks, and especially if you DO NOT overclock. Also, SSD caching rocks.
The latest AMD CPU lineup is only really decent after the latest price slashes, and the previous generation was not that stellar either (although more than ok for low-power laptops). Also, Ivy Bridge launches at the end of April, with significantly improved energy efficiency (max 77W TDP instead of 95W for SandyBridge or 95W to 125W for similar performance AMD CPUs).
I don't know how much you care about QuickSync, but for me, it's a GODSENT. Re-encode everything you want in mp4/x264 for tiny space and awesome quality noticeably faster than realtime, how can you not love it.
If anything, I'd say wait one more month and get a Core i5-3550S (the low-power version with 65W TDP, 4 cores, no HT, 3/3.7GHz normal/turbo). Should retail for about 200$. The built-in fan should more than suffice, especially in a decently ventilated case.
A generic Q77 motherboard will suffice, but depending on how much more it will cost, a Z77 mobo would be preferable. Both should support SSD caching (which gives you most of the SSD "regular user" speed benefits at negligible extra cost, since a 20GB SSD will do just fine in that role, or even a smaller one).
Z68 motherboards (most feature-complete for sandybridge, and the only ones supporting SSD caching as of now) start from as little as 85$, and pretty good ones from as little as 120$.
So I fully expect you to be able to get a decent mobo for about 100$, so a total of 300$ for mobo+CPU.
I personally would not skimp on the video card at all
Depends what you're planning to play.
I have a GTX 460 "v1" 256-bit with 1GB RAM and 675 GHz core frequency (factory-overclocked to 715), and I can play almost everything out today at max graphic detail in 720p windowed mode (I don't like fullscreen gaming anymore, no idea why). Skyrim ? Mass Effect 3 ? Piece of cake, excellent FPS.
Now they have a new version of the same out (almost all for sale now are the "v2" 1GB 192-bit, 778GHz base core) which is actually about 10% faster than what I have. And you can find factory-overclocked ones (to around 810) at 140$ (even 120$ with rebates, if you want to bother with rebates).
So about 440$ so far.
The one thing I would NOT dream skimping on is a nice airflow case with extra fans (the Cooler Master entry series is only about 40$, 55$ with all the extra fans you can possibly add on), and a quality medium-power PSU.
For the i5-3550S + Z77 mobo + GTX 460 1GB 192-bit, you'll probably only need about 300W of power tops (65 CPU, 160 GPU, 50 motherboard+RAM, 25 HDD/SDD/DVD), add a generous 30% "fudge factor" for the GPU overclock, CPU turbo boost, and quite a few years of old age, and you still will only need about 390W from your PSU.
I would recommend a CORSAIR "Builder Series" 430W PSU (the smallest they make anyway), it costs about 45$ and it should be more than enough for this particular build's needs, even if you decide to upgrade the GPU later on (as long as you keep the new GPU under 210W or thereabouts).
So that's about 540$ so far (100$ for case+extra fans+PSU).
Add a healthy 16 GB dose of moderate speed low-voltage RAM for 90$
...and you're up to 630$.
Pair a large moderate speed 2 TB HDD (130$) with a very fast 60GB SSD (80$) set in caching mode for lightning fast access for almost anything you use frequently, and you're in awesome business
Add some generic DVD writer for about 20$ extra.
Grand total : 860 USD for a totally rockin' machine.
At least, that's what I'd be building for myself if I wanted to buy a new machine in a month or two from now.