The FSP Hydro PTM 650 W is a power-efficient design that's reasonably priced and looks nice. However, competition in this segment is strong and includes the Corsair RM650x and Seasonic Focus Plus Platinum and Gold.
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