If you prefer better sound quality, pick the Gigabyte G1.Sniper M5. If maximum overclocking ability is what you're heading to, pick the Maximus VI Gene.
Anyway, a pair GTX780 cost just 1300$ and is less than 10% worse than a pair of GTX Titan ( 2000$ ), and if you OC then a pair of 780 can match a pair of Titan in no time, so you should consider lowering the graphic cards to a pair of gtx780. Doing that should save you a lot of cash for maybe a custom water cooling system without sacrificing too much performance.
If you prefer better sound quality, pick the Gigabyte G1.Sniper M5. If maximum overclocking ability is what you're heading to, pick the Maximus VI Gene.
Anyway, a pair GTX780 cost just 1300$ and is less than 10% worse than a pair of GTX Titan ( 2000$ ), and if you OC then a pair of 780 can match a pair of Titan in no time, so you should consider lowering the graphic cards to a pair of gtx780. Doing that should save you a lot of cash for maybe a custom water cooling system without sacrificing too much performance.