Crossfire 7870 XT with R9 280?

Hey everyone, tried looking up some information on this and it seems pretty scarce.

Basically, I'm thinking of doing a crossfire setup with my Sapphire 7870 XT which is this card:

Everything on the card says it runs a Tahiti chip set. Which should mean I can either pick up another 7870 XT (i've looked everywhere they're seemingly non-existent now) or I could go with a 7950 / R9 280... right?

Secondly, will a 750w psu be enough power to crossfire these? (I have an OC i5-3570k @ 4.2 Ghz fyi)

Here is a graph.

However the XT is not on it but the XT is a Tahiti chip and you can mix a 7950 and a 7970 so I would think it will work.

I am running 2 7950s on a 750w PSU no problem.

While I know the 7850, 7870, 270 and 270x all crossfire I am not so sure about the 7870XT to 280. The 7870XT is classed as a Tahiti LE and the 280 is the Tahiti PRO2. People have said they have crossfired a 7870xt with a 280x. Looks like you might be able to But I would wait for firm confirmation before spending the cash.

They still have the old CrossFire fingers so it is still older style like the 7870xt.

The only downside seems to be the fact that the Tahiti LE is not a full Tahiti chip like in the 79xx and 280 series cards so it would hold them back slightly. 

If none of this makes sense I am sleep deprived at the moment. 

you will probably be able to CF them, however in my opinnion its totaly pointless to do so. cause the 280X will completely holded back. and i expect that you will run into alot issues. with scaling. if its even possible!!

Maybe you even not able to CF them maybe, cause the 7870XT could have a diffrent bios..