I have another question for you, since you seem like a very experienced person when it comes to pc's. What gtx 980 should one get, the standard one with stock cooling, or one made by MSI, or a more practical one in my case is one made by gigabyte because gigabyte has a retailer near me. And what if I would like to water cool the GPU, would it make more sense to buy a stock one and replace the heatsink and etc with a water block or should I buy a 980 by gigabyte and replace the cooler with a water block because a 980 by gigabyte may have some additional features because it could be made possible with the better cooler. (Hope that wasn't too complicated).
Haha, believe me there are many others like me on LTT. They just might be asleep though if they're in the US.
I'm going to split my answer into two:
Air cooling: the reference design of the GTX 980 (in your case the Gigabyte branded version) tends to be preferred when doing air cooled SLI setups. This is because they have a blower style cooler which means that the hot air the fan blows is directly exhausted outside of your case.
With Gigabyte's non-reference coolers (G1 and the slightly cheaper Windforce 3X version) you get a GPU cooler that runs quieter and keeps the GPU temps lower. It also has a custom PCB that allows more overclocking potential. The Gigabyte G1 GTX 980 is currently the best GTX 980 out there. The drawback is that these 'open-air coolers' pump most of the heat into your PC case. You would need good airflow inside your case and with tightly packed SLI setups the top card will be hotter (although not by much) which most try to avoid. So both options would be good but it's up to you which one you prefer.
Water cooling: since you're going to be tossing the reference blower-style cooler anyway you might as well get the reference GTX 980 from Gigabyte when water cooling.
They're cheaper than the custom G1 and Windforce 3X coolers.