Thermal load/flow, and rad space question for CPU/GPU WCing

[Skripka]

Not a rookie, here. Just out of the loop and want input from people with experience with newer GPUs. Computer parts in question:

A) e3-1230, equivalent of an i7-2600 (non-K). Not OC'd meaningfully at all.
2) Coming upgrade to a Gigabyte Gaming GTX 980 G1 (got it 40% off retail prices)

WC blocks being used:

-DT5Noz on CPU, a king in bygone days of low restriction
-An Alphacool Nexxxos hybrid 980 block (basically one of the highest restriction blocks for GPU you can get) Review on a different OEM 980 is here
-D5 vario pump with alphacool top...have been running it at full power and it never bothers me when decoupled
-Mix of rotary fittings

I've skipped the last 2 generations of GPUs so I'm out of the loop here (see sig rig). From what I've read the GTX 980 cards are not that power hungry at stock...However this guy is getting OC'd a bit. So how much radiator space do I need for the above rig? Water flow shouldn't be an issue given how low the restriction is on my CPU block, and more restriction is probably a bit better to give my pump something to work against so it doesn't burn up (part of the reason for WCing the GPU here, and not just sticking with air cooling). I presently have TWO 2x120mm Swifty rads, I've been playing mentally with the idea of simplifying and only using ONE. What say the WCing board?

Sidequestion #1 with GTX-980 backplates...the card I'm getting comes with one already, any reason short of waterblock compatibility not to use the one it comes with?

Sidequestion#2 with GTX980s and these alphacool waterblocks, anyone point a fan at them to maintain airflow over the passive fins? My box will have airflow regardless

See the following picture for clarity (aiflow is from the viewers right to left): https://www.dropbox.com/s/ejaqtherx6yx4xy/IMG_0992.JPG?dl=0

 

[Tsumi]

The GTX 980 is a small die GPU, hence it not being that power hungry. The e3 doesn't put out that much heat. You could get away with only one radiator, it primarily depends on what fans you plan to run with it. It won't be near silent, but I bet you can keep it at reasonable temperatures with quiet fans.

 

[Erasmus354]

If you have two and can fit two in the case, I say use two. You will certainly be able to cool that with one without things melting, but your temperatures will not be great.