Is the ATI Radeon 5670 HD a really good choice?

So I'm saving up for a new GPU and a PSU that is good enough to power the new card. As of right now, the top candidate is an ATI Radeon 5670 HD. It seems like an awesome GPU. I've found it for 70 pounds (equivalent to somewhere around 111 dollars - according to online converters, which may be out-dated). I heard it also doesn't require that much power, and with that said - how much does it really need? I'd like my answer in watts and if you can, please include a recommendation of the cheapest reliable PSU available that would handle it.

Thanks in advance.

Some time has passed, but I have bought this card and a new PSU to power it. I can already say that the difference is incredible! Running Metro 2033 and Crysis maxed out... damn, I really do recommend this card to every PC gamer out there. With so much power for such a small price, it's value for money at its best.

if anyone is wondering what parts to get for there computer (gaming computer) which will be a high performance computer watch this video
https://www.youtube.com/watch?v=d_56kyib-Ls&feature=relmfu

It's at about 1:50 when he talks about what parts he's using, i'm guessing they're all good components, it's also a good video for building your own computer if anyone is interested