This would actually be a 'downgrade" as the 5870 is one tier below the 4870x2
"I don’t recommend upgrading your graphics card unless the replacement card is at least three tiers higher. Otherwise, the upgrade is somewhat parallel and you may not notice a worthwhile difference in performance."
1st tier - HD 5970
2nd - GTX 295 HD 4870 X2
3rd - HD 5870
4th - GTX 280, GTX 285 HD 4850 X2, HD 5850
Well I keep seeing that posted but to many articles reporting "notable" differences. My guess is tho, that as it matures, non reference designs hit streets and drivers improve differences will disappear.
But even if we do agree for the moment that they are comparable performance, $420 for no increase in performance is more than I'd be willing to spend.
hav a 4870x2 card and wanting to upgrade,is it worth buying the 5870 or must i jst wait for the 5870x2
No, it's not worth upgrading a 4870 x2 under any circumstances, unless you want to throw away a lot of money.
Yes, it's possible to get better performance over a 4870 x2. Minimal performance. But there is not any game out there where you can get appreciably better results from a practical gameplay standpoint.
If you're that anxious to get a DX11 card, just please relax. By the time a 4870 x2 is no longer top-of-the-line, they'll probably have come out with HD 6000 series cards, and you'll be cursing yourself for ending up with a 5870.
Of course, if you just have unlimited money and like buying new graphics cards, by all means, go ahead. Just ive you "old" one to me.