Looks like a great rig to me. The link you provided for the RAM says it's unavailable on that site, so I can't comment on that. However, I'm entirely in favor of the i7 and 16 gigs of RAM. Make sure the timing on whatever RAM you get matches up with the capabilities of your MOB. I'm set up with an AMD Phenom II X6, which is a fantastic processor. Though, if I had to do it over again I would most likely go Intel. They seem to have the edge, but AMD's prices are quite attractive. Good choice with the i7.
My sound card is wrapped in my interface (I use an M-Box). What DAW do you use, and what interface? I use Pro Tools, which currently is a 32-bit program (so I can only use 4 gigs of my 16 available in RAM). Consider that when you're looking at RAM, it won't matter unless your DAW can use it all (it must be a 64-bit program). That being said, there are some programs like Reaper and jBridge that allow you to host additional plug-ins outside of the DAW, though this only works for certain plug-ins (I don't think RTAS works, if I remember correctly).
I applaud your decision to professionally write on a PC. For 1/3 of the price you can have the capabilities of a Mac Pro (which is what I did as well). My apple-loving musician friends ridiculed me at first, but now I have the same computing capabilities and was able to purchase a ton of awesome virtual instruments as well.
Oh, and if you're recording live audio, you may want to invest in some good cooling equipment. Once you start running hot, you don't want a fan buzzing in all of your recordings.