that is really really unneccesary to have a dual loop for nb and gpu unless you added the cpu in with the northbridge and had loop1: CPU+NB and loop 2: GPU
If you want a cheap cpu block get a danger den TDX. they are a little older now but still effective, and cheap. picked mine up for £7.50.
If you have a mid-range gpu (4850/4870) i'd use the thinner radiator for that and a PA120.2 / PA120.3 for the cpu. dont worry about your gpu getting too hot if you use a MCR220, I ran a 4870x2 on one
The black ice series is thinner than the MCR220's by swiftech although they arent as effective. if space is an issue get the black ice - just make sure you get some high cfm fans (noisy!) Also you might want to get a pump/res combo for each loop in that case it would help a lot.
hope that helped!