I am assuming you are getting a pump top that holds the res? Or is a bay res that you can connect the pump to? Both are fine, in my opinion.
As for loop order, that looks good (I am at work though, so I cannot see an image if you attached it, so I am basing my comment off of what you put in text). Just make sure you are putting the res above and right before the pump so that it feeds it liquid and never air--looks like you don't have to worry about that if you are getting a top that holds the res, or a bay res/pump combo, though.
The major benefit of the XSPC rad is that it is thick and has a low fpi (fins per inch) so you can put low rpm fans (1k rpm) on it and it'll still perform, but I think the EK should be okay too--it has 10 fpi and the xspc has 8. The EK is around 10mm thinner, but I would say you should be fine with GT AP-15s cooling the EK rad since they are 1.8k rpm fans and you can always run them at a lower rpm and turn them up with a controller until the EK rad performs the way you need. You may need to run your fans at a higher RPM with the EK than the XSPC, but AP-15s aren't even that bad a full speed, so I wouldn't worry about it. I just run mine full speed when gaming and don't worry about it, and turn them back down when doing normal computing, they are that quiet.
Oh, and my water cooling loop still heats up my room, it's not only air cooling or dual card setups that do that; the heat still needs to go somewhere, so it goes wherever your fans are blowing the air out of the rads. I have two gaming pc's (both water cooled) in a medium sized room and when my gf and I game in there, or just one of us, I need to turn off the heater and open a window because it gets overly-warm in there if I do not, and they are both single card setups. So I would still expect your rig to heat up you room, even if it is water cooled.
Post pics when you are done! Cannot wait to see it.
Edited by svthomas - 6/3/11 at 9:41am