The good news: all the parts have arrived, and I've blocked off most of the day to build the new system.
The bad news: first problem (really didn't see this one coming). The damn Nexus PSU is a couple mm too big. Since modding the PSU case is not my idea of a fun time, I'm left with either a) returning the PSU and ordering one that will actually fit my case, or b) modding the case to make the PSU fit. I think I'll go with b, after I test the PSU to see if it is as quiet as I hoped. Out comes the dremel! The cover looks like it will stay on ok. Any other ideas?