Your system can handle it, what you're really asking is what kind of temps you can expect, and there's just too many factors involved to answer that accurately.
It will work. Many people have this setup.
Check it out
If anything, I would question the use of BIX in a pelted system: it looks (to me) like a conflict between form and function. Your coolant temp could drop say, 5 to 10 deg C with a better cooling solution (which may have a negligeable effect on CPU temp: 1 or 2 deg C). This assumes that your coolant temp will rise above the 27C you're getting now: it's not possible to cool below ambient.
Personally, I'll pick a big fat heatercore over spending $100 for a couple of BIX, anyday (but hey, that's just me!).
As for the second loop, because you use the two rads in parallel (versus one), the flow rate will actually increase (through the GPU block), because the two BIX will be less restrictive than one.
I wouldn't bother too much with the GPU pelt: it's really overkill. You're far more likely to damage the VC than getting better performance out of it for any significant period of time. You can use whatever pelt you want, but keeping the power down is always a plus!
Since you just want a quick-and-dirty score, go ahead and cool it as much as you want (at your own risk, of course!).