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7870 XT @ £200
The GTX 660 is not going to be a 'huge' step up from the 560ti 448.
You need to be looking at Radeon 7870 XT as above ^^.... GTX 660TI / Radeon 7950 / GTX 670.
lol they only have to replace performance not cost.
@Its_Me: A 7850 roughly matches a 560Ti 448 IIRC so if you can wangle a custom cooled 7870 you've done a good job.
A 660 is equivalent to a 7850 and a 660Ti is equivalent to a 7870 to give you context from the nVidia side. Think a 660Ti will be too expensive for them to issue as a replacement.
He's not buying - they're replacing with a different card from stock.
lol they only have to replace performance not cost.
@Its_Me: A 7850 roughly matches a 560Ti 448 IIRC so if you can wangle a custom cooled 7870 you've done a good job.
A 660 is equivalent to a 7850 and a 660Ti is equivalent to a 7870 to give you context from the nVidia side. Think a 660Ti will be too expensive for them to issue as a replacement.

So a 7870XT would be the best choice, followed by a 660.
ok, thanks.
7870XT (no chance IMO)
660Ti (equally no chance)
7870 (probable with pushing)
660/7850 (standard option)
Why no chance on the 7870 XT?
.Because that would be a large performance increase. They only have to give you an equivalent card in performance terms not monetary terms.
A good manufacturer/retailer may give you a little bump if you're lucky.