Where did you get 5-6 years from?
From me stating hardware lasting 5-6 years is a dream and doesn't happen in real life. And by that i meant, adequate performance and driver support. Then you two clowns reply with "my blahblahblah is bought in 2009...." Chances are you didn't even buy it in 2009 and even slimmer that you bought 2 for CF.
BTW the maximum possible time you could've possibly own a 5850 is only 3.5 years. That's about 2 years away from the 5-6 yrs estimate.
Huh $700 ????
The release price of the 5850 was $259 each.
Yes MSRP was 259 for 5850 1 GB card at launch. The only cards available to buy were the $350+ ones and those didn't last long either. Unless you preordered or sat on the comp waiting for it to pop up on newegg, you most likely couldn't even buy one without the 100+ premium. Weeks after launch, prices went back down to the high 200s.
Even a single 5850 is as powerful as some of the midrange cards today. A single 5850 would faster than the ATI 6850, GTX 650ti and on par with the 6870 and 7790! Even as as single card its fast enough to play today's games at high not medium.
Infact, crossfired the 5850 is actually a fair bit faster than your 7850, even with its age and glitches
A single 5850 is slightly faster than a 6850 at launch because AMD switch the numbering system. After patches, 6850 seems to be slightly faster on the newer games with newer engines. AMD had already stopped supporting 5000 series. In 2 years, you have to be retarded to keep using it.
A CF 5850 will be marginally faster than a 7850 while having plenty of bugs and wasting energy. I paid $140 for my 7850 after $20 MIR. I can buy 8850/9850/etc... every cycle and still come out much less than 2X high end cards and hoping for it to last 5+ years.
Let me fix your statement. "Infact crossfired, 2 X 5850 is actually a fair bit faster than your 7850, if CF scales correctly and there are no glitches"
Back on topic
He asked for a solution that will work for 5-6 years without changing parts. The answer is that is not possible.
And no spending a ton of money now just to have so-so performance in 5 years, no driver support, glitches/bugs, and burning up energy like crazy is not considered working.
Stop giving people bad advice.