since you already have a very nice GPU i think garethman's build is great. however im not sure of the PSU's brand quality, i'll check Ceew1's guide and go from there.
its not a very large budget, so it is best to focus on the parts that will get him the most FPS, instead of slightly better looks. usually modulars come at a higher price range for a similar PSU.
Well from experience with the power supply, I can say it is the best one I have ever owned. Although I am positive that there are better ones out there.