Yeah, the 'channel' stuff is all nonsense. Three of the same stick will run in 'triple' channel just fine or you can just go for a dual channel kit. It makes next to no difference in games.
Most X58's can run in flex mode too. You can usually put whatever DDR3 ram you want in there - if capacity is all you care about.
At this point I'd recommend you just get a common 16GB dual channel kit. Having recently gone from 6GB(C7/1.65V/Triple) to 16GB(C9/1.5V/Dual) myself I've not noticed a degradation in performance. The benchmarks I ran did come out in favour of the old kit, obviously, but I needed more capacity. Being a few percent slower in a benchmark doesn't bother me.
This is the kit I picked up for my old EX58-UD5. BLS2CP8G3D1609DS1S00CEU. It was only forty odd quid in a sale.