Between the two GPUs you posted, GTX460 is way better. The GTX460 is the most popular card in the new Fermi line, and with good reason. It's the BEST bang for your buck. (SLI two of them, and you out-perform a GTX480!)
Comparing the 5770 posted with the GTX460 posted price wise, they are extremely close. The 5770 is $135 after $20 MIR (free shipping). The GTX460 is $132 after 6% promo code discount and $25 MIR ($2 shipping).
As you can see, you are going to be paying $3 less for the GTX460, a card that outperforms the 5770 utterly. See here for proof:
http://www.tomshardware.com/forum/29...770-benchmarks
As for power issues, the GTX460 and 5770 both recommend a 450-watt PSU. This DOES include all components already. There is NO WAY a GPU can draw 450-watts single-handedly. 550-watt PSU is perfectly capable of the upgrade you will be doing. You have 100-watts more headroom than the "test" setup they used to obtain that 450-watt recommendation value. Use this calculator for added re-assurance:
http://extreme.outervision.com/psucalculatorlite.jsp
Lastly, as for correct cables, the GTX460 does require 2 6-pin 12v connectors. The 5770 only needs one. Your PSU came with a 6-pin as well as a 6+2-pin (this means that you could utilize a card that requires 1 6-pin and 1 8-pin, too). (This also means that the 6+2-pin can be used as just a 6-pin!) So, that means your PSU does support a card like the GTX460 power-wise. The GTX460 you have listed DOES come with Molex to PCI-E converters.
The only issue is that you will need 4 available Molex cables to run the card. However, if you are referring to the "8pin" as the "6+2-pin", then you can use that one, as well as 2 available Molex connectors attached to the converter it will come with, to fully power the GPU.
Sorry for all of the text/information, but it should be of some help
Feel free to continue to ask
any questions!!
EDIT: I also wanted to take note that the new AMD 6000 series is coming out within the month, so you might as well wait for that as you might have a better choice of card from the latest line-up. The worst case is that you end up with a 5000 series at a cheaper price
