That's a very good design Zoson. Glad to see you're taking the plunge!
Personally, I'd drop the whole wiggly channel around the central area, but if it's wide enough, it won't hurt anything. It certainly doesn't improve cooling though.
You design demonstrates the convection effect, optimized with coolant flowing through the fins.
It might be a little more restrictive than you think though: even if the cross section between the fins is equal in area to that of a 1/2 ID tube, you have to convert each channel to its hydraulic equivalent. You can find the calcs here:
http://www.lmnoeng.com/pipeduct.htm
There's also an "orifice plate" type of restriction, as the flow is split, entering the finned area, and leaving it.
The rest of the flow restriction will come from the 90 deg bend at the inlet, and through your wiggly channels.
As for cooling, it'll work very well, based strictly on the convection effect, and the flow rate. Using a higher flow rate shouldn't improve things a whole lot, so this'll work with a relatively small pump.
If you've been following Cathar's design, then you should know what he did: he throttled the inlet so that it would shoot water down between the fins: this adds turbulence, and improves cooling even more. There are other ways to do this.