I currently have 2 4870s in Xfire (16x/4x) and eventually thinking about an upgrade. Would the 7850 be significant enough to justify $250? That's about what I'm willing to pay. I've been debating this since Tom's heirarchy put's an x2 on par with a 7850 (besides power consumption, DX11).
I upgraded from crossfire 4850s to a 6870 (which are supposed to be about the same) and am much happier with the 6870 than the crossfired 4850s. Most of this is because of all the driver problems that I had with crossfire and the much lower temps I have with the 6870.
I didn't see that chart you're talking about but the 4870x2 has no place being in a chart next to a 7850. they are 2 completely different animals. until people stop looking at Frame Per Second as the SOLE purpose of performance too many are going to be swayed by inaccuracy's.............
I came off of 3 4870's to a single GTX 480 and was very impressed by the performance. Unfortunately, a 480 is more of the same as far as heat and power consumption are concerned. EVGA's reference 480 is on Newegg for $220, which is really hard to beat. I honestly think you'll be satisfied by a 7850 if you should choose to go that route. It'll be a lot quieter and run cooler AND you get all of the DX11 features as well as Eyefinity. Plus, you rid yourself of the driver issues associated with multi-card setups.
4870 x2 is slightly worst than a 5870. A 5870 is roughly the same performance as a 6950 or 560 Ti. Both of those cards are a fair bit worse than a 7850. Plus you get DX11 and 2gb of VRAM. Especially if considering going with a bigger/multi-monitor setup in the future, the 7850 will really blow a 4870x2 away.
Thanks for all the input. It seems like it would be a positive change, but I'll still wait a bit until at least the GTX 660s come out to see how they fare, and maybe 7870s will drop more by then. I'd be curious to compare everything like min/ave/max FPS, 3DMark, heat, power, noise, micro stuttering, and overall feel between old gen and a new gen card. If I can I'll post again. Maybe others are wondering the same thing based on that possibly misleading Tom's heirarchy.