Alienware X51 R1 GTX666 Question

Hi there. I have an Alienware X51 R1 with an i5-3450 and Nvidia GT 545. I've recently been thinking about upgrading my graphics card to the GTX 660, which I have been told is the best graphics card the X51 R1 can handle. I know that to do this, I'll have to buy the 330W PSU from Dell also. I do have some concerns however: I have been told that as the X51 is a small PC, there may be some difficulties in finding a GTX 660 that will fit in my machine. So could anyone tell me which versions of the card will fit in the PC? Also, I've heard that using the 330W PSU and the GTX 660 in the X51 R1 can present some power consumption issues with USB powered devices such as my phone or my Razer headset. Is this true, and if so, would purchasing a USB hub with its own power supply resolve this issue? Could anyone recommend a good, relatively cheap-ish hub? I just don't want to drop £200+ on the new PSU and card if it's not going to work. Thanks for your help.

Hi FAFFYWAFFLE ,

I believe it would be better if you check and if required join this discussion below:

Alienware X51 Graphic Upgrade discussion

Hope it helps.