Ok, Ive ordered myself:

MSI R9-280x x 3
Seasonic 1250w Gold PSU

These 280s are the best I couldve gotten hold of in the UK now without a wait time for the RRP (the toxics are sold-out and the Asus is over £50 above RRP). After much research (and help in this forum) I thought this PSU was the best bet in terms of reliability and future upgrades.

Now my question is:

Which motherboard for this setup?

ASUS M5A97 - 2.0 - motherboard - ATX - Socket AM3+ - AMD 970
Gigabyte GA-990FXA-UD3
Asus Z87-Pro S1150 Intel Z87 DDR3 ATX
Gigabyte Z87X-OC S1150 Intel Z87 DDR3 ATX

Listed in order of expense - low to high.

The Asus Z87-Pro has integrated wireless so I won't need an adapter but won't something cheap like NETGEAR G54/N150 Wireless USB Micro Adapter WNA1000M do the trick?

Im interested in people's thoughts before I go ahead?