I am doing something similar with my Corsair 650D. Cutting grills and such too and adding the foam. I'll be going for a Coolermaster Megaflow in front since I don't need the HDD bays at all (just putting an SSD in the 5.25" bays). For the rear I was almost gonna buy the same Noctua, but I will try and fit the Thermalright TY-140 fan instead. CPU cooler is going to be the Thermalright Archon.
Yeah, I thought about that -- there's no reason the hard drives *have* to be in the lower bay, and in fact I have a "scratch" SSD sitting on some foam under the DVD drive. If you only need one or two drives (technically, I have three: boot SSD, large data, and scratch SSD) then that does make sense and would remove another obstruction from the front lower fan. No drive bays down below at all...
The main difference is that I will have a low RPM 120mm noiseblocker as top intake to add a little extra cool air to the CPU cooler (overclocking), but are you finding temps great even with dual graphics cards? Because I'll likely go for a dual-card setup as well, and was worried the temps might be too high to get a good overclock on low RPM fans.
Temps are very, very good with the pictured configuration. Note that I do use the built-in fan controller hooked up to front and rear fans, and I turn it up when gaming or doing furmark+prime95 tests. But my furmark+prime95 results are quite good, only hitting 83c video and 75c CPU under what I consider to be a totally artificial level of load that I'll never see in real life, ever.
For example, during typical high end gameplay I see ~400w power usage, but with furmark+prime95 it's 620w.. that's a 50% increase (!!)
It wouldn't hurt to have some kind of low-RPM fan blowing around near the memory, but I doubt it is essential unless you are somehow hitting those prime95+furmark numbers in normal use and it stays at that level for hours.