I just bought a new pc (Gateway DX4860-UB32p) to play SWTOR mainly. I installed my ancient 7950GT card and while the game runs it looks pretty bad. I'm certainly looking for an upgrade in this area and have my eyes on the cards listed above.
Budget - want the most performance for the $$, don't mind spending a little bit but don't want to waste it
PSU - only a 300w psu. These above listed cards have requirements of 400w+ but I have read of many people running them on 300w psu's with no issue?
I really don't know too much about those particular cards. I will say that you should definitely stay within the power requirements. It is really not good to be pushing the limits of a PSU. I mean, it has spelled bad news for people before - especially if it's a low end PSU. I strongly recommend an upgrade there.
If I had to give you some advice on a GPU, it would be to go with the 6670. Here is a video of a guy using the 6670 to play Crysis Warhead, of all games! And nearly maxing it!
A 6670 will run as far down as 300W on a name brand PSU. Prebuilt systems tend to use poor quality PSUs, so I would recommend a PSU upgrade as mandatory. The HD 6xxx series is usually the better option for gaming until you're spending a lot on high end cards. How good a card you need depends on your resolution and quality.
Yeah, I agree with both above posters. It is just a different series, same DX11 support (in theory). Just like the 6770 is basically a newer 5770 (however, I would take the 5770 over the 6770, anyday).
And you are going to need a PSU upgrade.
Also, I wouldn't expect too much out of the 6670. It is what some would consider a low to mid range GPU. It should be fine for SWTOR. If I had to guess, I would say you could run it in 1280x720, high settings and AA off and do so with ease. Perhaps even 60fps at those settings. Maxed out in 1080p, I would guess that you would maybe get 15-25fps. My estimates have proven to be dead on in the past, so when you get the card, remember what I said.