i would stick with the server memory for the ECC and since the board can handle 144GB if you use registered ECC memory and only 24GB of desktop memory, this gives you expansion room for memory (if you filled the board with 6 sets of this, 72GB)
in desktops Super Talent is so-so, but this is server memory which is better quality
I have a workstation built on a slightly older supermicro board and actually own 2 of the model X7DWA-N. I put 32 gigs of ram in it. I recommend you consider going with Pc Power and Cooling for your power supply... get the 1200 watt unit. I have 24 hard drives connected 2 it plus dual X5482 Xeons and it runs very fast and very smooth.
As far as your motherboard, I think you picked a good one.
I'd also like to suggest, if you want to get optimal performance that you consider getting a dedicated RAID card. Areca technology makes some outstanding models and I have owned 3 so far and am very impressed with the speed. Which model you get depends on how much money you intend to spend. I currently use the Areca ARC 1280ML which has 2 gigs of dedicated cache on it and I'm getting insane speeds. Since you are going with a workstation board you may as well go all the way, right?
As for ram, I agree with mindless that you should stick with Registered ECC memory... it will definitely give you an upgrade path. If I were you I'l put in 24 gigs of ECC Registered memory... which will give you plenty of room to grow. From one computer guy to another, let me know what you decide to do I'd love to see benchmarks of that system!