I have a Gigabyte H77m-D3H Motherboard which has a x16 pcie and a x4. I am curently running my 7870 in the x16 and was wondering if i crossfired what would the difference be between a x4 config in comparison to a x8 or x16? Would it even be worth it?
x4 will probably bottle neck the second card. I don't recommend multi card set ups anyway. Always get the fastest single gpu you can afford. That card is still very powerful and should be able to play most games at high settings at 1080p.
x4 is... yeah, you're not going to get good performance from that at all.
Besides, the only time crossfire or SLI is worth the trouble is when you need more performance than the highest end cards can put out - it doesn't double your power, there's still microstutter and driver issues, and, oh yeah, it doesn't work in about half the games out there.