I'm looking for some advice about upgrading to a GTX560Ti from an HD6770. I don't really know a lot about how to interpret the different specs of the varying models of the 560...all I really know is that the 560 will be a significant upgrade.
The thing I'm most worried about is the power supply requirements and the cooling requirements.
My budget is $300 max, and would prefer to keep it within $250 before tax, so I'm hoping I can just swap out the graphics cards without having to buy a better PSU and cooling.
The problem with prebuilt systems is that the manufacturers cut corners to keep their cost down. The PSU, being number one. It has just enough power and connectors to run the system as it is. They also never put "name brand" units in their PC's.
So while 460W sounds good on paper, it might only have 250W on the 12V rail and might not even have a 6-pin (let alone two) to connect to a Video Card.
I don't know exactly what that means for me, but I hope it will suffice for a newer card :S
What brand is it? Just because it has the ratings doesn't mean it's all that good (I'm looking at you CoolerMaster). It's within your budget to upgrade the PSU as well as the GPU. I recommend doing so. A good PSU will carry you through any other upgrades you decide do including later on swapping to new case, upgrading the Mobo / CPU / RAM and possibly going SLI.
The 560 Ti also has a power draw of ~263W at load. That will cripple a crap PSU.