Stamp of approval. (Though I don't care for many of your choices, they're still solid.)
However, if you want to do crossfire, don't. :P
Get one single, better card, for two reasons:
One - an h77 board will bottleneck a second card.
Two - Xfiring a 7870 is barely on the borderline of what would be beneficial. Crossfire with low-end cards simply isn't worth it because of the fact that about half the games out there don't support it, it doesn't actually double performance, and it's got a LOT of issues compared to one card.
I'd recommend sticking with what you have, and, when you have more money, selling the 7870 and buying a good card from the 8k series that'll be out by then.