I agree with the above statements. The 5770 is, IMHO, a lot more bang for your buck if you're just willing to spend a tiny bit extra. It's more than worth it, and the 5770 will last you quite a bit longer than the 5670. It's of course up to you, obviously, but it's sort of like this - getting the '670 will save you maybe $30 now, and cost you another couple hundred in the future when it becomes worthless and ultimately nearly obsolete. The '770 is probably going to be relevant for at LEAST another 1.5-2 years, by my estimate, and you could probably even squeeze a little more juice outta the '770 by overclocking it past stock rates later down the line. That won't really be NEEDED (if it ever is 'needed') until a while's off though.
IMO, that is why brand name really IS king when it comes to PC parts; a lot of brands are known for faulty parts for whatever reason - other brands are known for grade-A quality. The top dogs when it comes to ATi are, IMHO, a. Sapphire or b. XFX. TBH the only nVidia GPU manufacturer that I have much experience with is EVGA... and they are by far the cream of the crop for nVidia from the other brands I HAVE tried out.
Same brand as the 5670, not that I recommend it - Diamond [out of stock ATM]:
Diamond 5770 1GB
The brand I DO recommend - Sapphire:
Sapphire 5770 1GB
I kinda wish we could get the Vapor-X edition without having to purchase the combo. I've heard that V-X has superior cooling capabilities on the GPU unit itself. That aside, Sapphire is a really solid, reputable brand, and
XFX's 5770 is pretty nice too. I've never really heard of Diamond as anything more than a cheaper knock-off of Sapphire (no offense Diamond fans, correct me if I'm wrong!).
EDIT:
Really? For some reason I was thinking only the 5770 and better were DX11 capable.
Nope! Thankfully it's the entire 5000 series.
... It is made possible by the ATI Radeon™ HD 5000 Series of graphics processors and the new features of Microsoft? DirectX? 11 technology ...
[Source]
This makes DX11 available to pretty much every gamer, which I think is the beauty of it compared to equivalent nVidia cards which IIRC -- until recently, didn't tote DX11 as a feature. I don't intend to knock nVidia though as I love their cards. Especially EVGA. EVGA makes delicious cards.