So here's what I've got configured so far. I've gotta pay a nunch for taxes this year

So I'll likely only get this in July.
Here dem specs.

Didn't include a PSU because I have no idea if I need a mATX one. Some people have told me you don't. Cause the highest wattage I found for an mATX PSU was 400w.
Other than that, how's she look? Will everything fit and play nice together? Is that Motherboard even Crossfire compatible?