If you want to try watercooling out of personal curiosity or you want to do some heavy overclocking, the go for it, its very fun part of building and testing a PC, but if this are your priorieties,
1 quiet and reliable
2 no maintenance
Aircooling in most cases will be quieter, i never seen a quiet pump. Reliable, aircooler has less part, its pratically just a fan, while on the water cooling you will have the fan or fans, the pump, the rads, resorvoir etc, even on prebuilt, you will still have more parts and the risk of introducing water to an electric ambient, the risk of rust and leaks over time... etc.
Prebuilts like Corsair H100i are nice, but big air coolers like Noctua NH-D14 / Thermalrigth Silver Arrow are up to par with it, and less noise, less moving parts, less risk of failure. So if you want to go with watercooling without going too deep, check Swiftech H220 Compact Drive II Plug-and-Play Liquid Cooling System
, its a prebuilt (not 100% maintaince free), but you can grow on it, you can later add rads or introduce your GPUs, motherboard heatsinks, etc, its performance is much better also than any prebuilt on the market.
With that said there are tons of people that go for it, and are happy, its a hobby in its own, and they have great success, but the for me its more for performance and overclocking heavily than Quiet/reliable setup. Now if you already entering watercooling, why not cool the gpus with it also, you already introduced the pump noise, might as well have the gpus cooled by the water loop, and avoid the extra fans on the each gpu and the heat inside the case that the gpus will generate, would be better to have the heat being dissipated by the rads where you can have 120mm fans that wont interfere with the width of the cards, and this will open almost all standard cases, as you wont need a huge case, as the gpu would not be triple slot. A mobo like Asus Maximus VI Extreme
coudl fit twin GTX780 + dedicated LSI card + dedicated soundcard, still on ATX factor, with a fractal design define R4 and just open the moduvents on top to add the rad, the R4 will also have enough space for all your hdds. On the event that you will want a case with more space, then look into Antec P280 Black Super Mid Tower Computer Case
(has space on top for 240mm rad and supports XL-ATX mobos) or Fractal Design Define XL R2
(similar to the R4 just bigger and supports E-ATX and XL-ATX mobos).