Most cost effective upgrade path

[NoNameNoNumber]

So I have 1 Asus Gtx 560 Ti 1gb playing Skyrim, Hitman type stuff on this BenQ monitor http://www.overclockers.co.uk/showproduct.php?prodid=MO-080-BQ&groupid=17&catid=510

Rest of the spec:
2500k/Z68/8Gb DDR3 1600MHz/Corsair 550W PSU

Which option might you suggest.

1)Buy a new PSU and another Asus 560Ti to SLi

2)Replace the 560 all together and if so, to what? Would a see enough of a benefit from a 660 or the likes? And would my PSU be ok?

Thoughts much appreciated.

 

[NoNameNoNumber]

7950 looks good actually, how much are those games fetching? I guess I'd still get maybe £60 for the 560...

 

[NoNameNoNumber]

Sweet, Mine's a VX550W, perhaps not their greatest but has been faultless for me.

 

[NoNameNoNumber]

Should I wait for the new cards to come out before purchasing or are these 7950's not going to get any cheaper?

 

[NoNameNoNumber]

OK cool, Should I look to sell the games on here? are they steam codes or what?

 

[NoNameNoNumber]

I'm in the MM

Ok thanks for your help