What is the advantage if I go for two-way SLI with the 760 over one 780? Or would it be enough with one 770?
You dont need to do 2 way but if you do 2 way you dont have as many heat problems. Also at the price of that titan I would do 2 way SLI 770's and you would have a BEAST PC! I dont know what games you will play but you would be pushing like 400 FPS on minecraft with a 64 bit texture pack on max settings probably. So there really is no reason for two-way SLI except heat control. Its your choice you may get better performance out of the two-way SLI with the 770's but its up to you. If it was me I would do two-way SLI with the 770's but if you have your heart set on that Titan go for it!
I never had my heart set on the Titan. I couldn't make my mind up. I was going to get one 770, then I thought about a 780, ater that I was considering two 770s but wasn't sure. then the 660 recommendation came up and now my mind is all over the place.
Although I did say my price was £1500 I still haven't decided. It will definitely be a minimum of £1200, though.
I think the build in your original post is great. Only change I would make though is the sound card. You don't need one. Unless you are engineering music with studio monitors, you won't notice the difference. My motherboard's Realtek on board sound is terrific .
Also, I see post about problems with Creative sound cards all the time on here.
I'm actually considering either getting two GTX 770 cards or two/three R9 280x cards. I'd rather stick with nVidia but does anyone think the AMD option would be better? Also, I'm going to drop the sound card and the SSD and probably get some better RAM.