^+1. It's an absolute no no for splitting up the flow. That kills your flow rates.
The ideal set up will be to have 2 loops.
If you can't do 2 loops:
res>pump>CPU>220/320 rad>GPU>320 rad.
Do you think that just one pump can push such a loop? Would the Koolance PMP-450 or the Swiftech MCP355 be strong enough to push adequate pressure through two waterblocks and two radiators?