llkashll :
290 cfx is still inferior solution to 780ti crossfire, it competes well against 290x cfx so long as its overclocked but that relies on OP wanting to install a custom cooler since many reviews have demonstrated significant thermal throttling on the r9 2xx crossfire setups. Given that crossfire is limited by the lowest clock average performance is going to be diminished over what he would see with a stock gtx 780ti crossfire.
Also given OP would rather a single card upgrade over a dual card repurchase it leaves the 780ti as best suited to his purposes.
I definitely see your point and I would be tempted for a r9 290 cfx setup for the value, but it largely comes down to OP's choice of NVIDIA v ATI.
290 cfx is not cut and dry inferior to 780 ti SLI...........its all program dependent. Some games and programs run better on AMD platform, some run better with Nvidia. And in reality benchmarking is hair splitting and many times does not even translate to real world PERCIEVED performance.
For example. I can run SC2 HOTS on my AMD based laptop(2 6990m AMD cards in Xfire)and rip out about 80-90 FPS with all settings maxed out. I can go over to my friends house and play the same game........on his Nvidia based laptop with a GTX 675MX he gets about 50-60fps.
Being able to tell the difference between em.............very hard, even when playing side by side.........even though I have about a 50% performance advantage over him.
Benchmark performance #'s and what we perceive in real world are 2 different things. Benchamrking tends to artificially inflate what we actually perceive. Many times that big performance boost translates into 0!
Again, the R9 290 and 290x in many games and apps outperform the Nvidia 780/ 780 ti / titan. It all depends on the game/application being run. There is no clear cut winner, and many times the benchmark winner isn't really a winner at all when it comes right down to it.
Which is why I think the OP would serve himself best going with a pair of 290's now for the money.........no point waiting.........and waiting.........and waiting.........and then spending ALOT more money for no REAL WORLD appreciable difference in many cases. These are all SAME GEN cards which all have similar performance capabilities. So get the best bang for the buck now and ENJOY! =D
2 years ago I got my current laptop with my xfire 6990m cards. Paid a good price for it...........have been playing SC 2 now for 2 years maxed out with all the eye candy having a blast. My friend decided to wait an extra year before upgrading his laptop, and stuck it out playing a lower resolution with low quality effects to keep it playable, he hated it, but he waited. He ended up paying more for his single card solution waiting on all the hype and promise...........which never really materialized he found........he plays with all the eye candy now and at native 1080p resolution, but still doesn't get anywhere near the hyped performance he expected in benchmarks and on some games in real play. Yet he wasted a years worth of his time and life patiently waiting for the next big gpu generation and now wishes he never did wait and picked up what I did WHEN I did.
Something to ponder for all.
Im not part of the AMD camp or the Nvidia camp, I am part of the best bang for the buck NOW camp. And in reality its the camp that ALWAYS WINS. =D