The ASUS GTX760 DirectCU Mini OC is without a doubt the fastest graphics card in the world that's shorter than 18 cm. So if you're looking for a powerful graphics card for your compact Mini-ITX PC, this ASUS card is a good option. It's just as fast as the full-size GTX 760s, and only slightly more expensive. The only trade-off is the amount of noise the compact cooler produces.
Slow computer got you down? Maybe a hardware upgrade should be in your cards, if so this guide to the Fundamentals of Upgrading a PC is an invaluable read. PCSTATS Tips