Couple of Water Cooling Questions

I'm planning a new dual-loop water-cooling system for a computer that I'll be building in December when I return from Iraq. I intend to get the lasting components (Case, PSU, Cooling) first and wait until the last minute to pick out the core components (CPU, GPU) hopefully to avoid buying components that will have upgrades available in the near future.

My plan for the loops is as follows:

Loop 1
Reservoir (XSPC Dual-Bay w/2 internal pump mounts)
Pump
CPU Block
Northbridge
Dual 120mm Radiator
Reservoir

Loop 2
Reservoir
Pump
GPU
GPU
Dual 120mm Radiator
Reservoir

I had in mind a gigabyte board with an integrated water-block on the northbridge, however the fittings are 1/4(3/8?) and I'm concerned that transitioning from 1/2 to smaller after the CPU block might restrict flow more than I'd like, as well as the different metals involved (I believe I read aluminum, instead of copper). I may need to change motherboards, and purchase an aftermarket northbridge/mosfet block set. Perhaps a replacement block for the board that integrates into the same mounting area with 1/2 ID fittings, but I haven't been able to find one anywhere. Any suggestions?

I'm fond of the dual-bay reservoir design with the two pump mounts by XSPC, however, never having seen one outside of pictures it seems the return dumps the water right back into the pump inlet, allowing little circulation of the water in the reservoir. Is this a valid concern?

I'm deciding between a pair of Swiftech MCP350 or MCP355 pumps. Any comments on the different noise levels would be appreciated. I'd also like to know how much of a cooling, benefit the increased flow from the more powerful pump would give.

Any advice would be greatly appreciated.

I have read that, and many other intro to water cooling posts and articles from many sites. I've helped build a couple of water-cooled systems with friends before, but that was several years ago, well before the vast availability of specialized parts that are around today (much to my joy). My questions are related to specific hardware that I am hoping to find someone who has experience with.