Wow you have an excellent warranty!, here in my country all that you get is 6 months, and if they don't have a replacement you have to wait, 2 or maybe three months because they will not return your money, warranty here sucks!.
CUDA miners weren't profitable until the maxwell architecture that arrives (in my country) in early 2014, so, as soon as I saw the results ppl here where posting about it, I start selling all my AMD cards to buy maxwells (still do, I still own a great deal of 7950s (with custom, low voltage firmware)), and as soon as I sell enough I will buy more maxwells
for what I have read, 750ti seems to be the king, because KH vs Power consumption is the best, 970 is a huge beast, fantastic card, but eats too much power, and in a place where power is expensive it's a no go.
ZOMG! 4K USD/mo in electricity! YIKES!, when I had the complete farm in operation with scrypt (38MH), I was under 1K USD/mo bill and I didn't pay any rent for the space because it was borrowed
no wonder why you didn't get ROI, between power costs and rent, eat's all your profit
geez...