You can fit 780 Ti's in mid towers
http://www.newegg.com/Product/Product.aspx?Item=N82E16811139009
http://www.newegg.com/Product/Product.aspx?Item=N82E16811139010
Fits 316mm with upper HD bay in place / 452mm with bay removed
Asus tends to have some of the longest
Asus 780 Ti = 10.8 (274mm)
Asus 770 DCII =10.7: (272mm)
Asus 760 DCII = 8.6" (218mm)