ASUS' new GeForce GTX 580 DC2 uses a massive triple slot Direct CU II heatsink that increases cooling performance significantly. As a result the card is extremely quiet in both idle and load - quieter than many midrange cards. ASUS has also increased the operating clocks of their design, all this for a small price increase of $5.
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