crossfire issues will always exist, imo. it is always favorable to go single gpu (in both camps).
2 7870s will be more powerful for sure. even more powerful than a 290 when oc'ed. prolly even. i've read one member asked the same question who already owns 2 7850s and the np stated that there are currently no issues running crossfire. zero issues. i've tried crossfire 7950/7970 and had zero issues but i only played BF3, C3, and C2. games like FC3 is a different story. my advise to you is to shoot for a 290 for a few more bucks or a 780 if you want to go green.
edit: in short, a jump from a 7870 to a 280 is really minimal other than the add'l vram.
Edited by rdr09 - 11/9/13 at 7:25am