I never cared for USB powered coolers I have owned all off Dells Highend laptops 9100, XPS , XPS Gen 2 and currently the XPS M1710 and have used laptop legs on every one and beleive me they do work it lifts the rear of my laptop to improve airflow and also puts my laptop on a good angle for typeing.
http://www.laptopdesk.net/access-legsf.php
I have a D-Dock I now use with my M 1710 but still have the laptop Legs I had to put the Laptop Legs in a special spot and drill a hole for the wireless card screw and trim a little with a dremel so the Laptop legs would not interfear when docking but worth the 10 Minutes of drilling a whole and triming the Laptop Legs as they are a great product and do work. I also use 3 M weatherstriping glue rather then the 2 sided sticky tape that comes on the Laptop Legs to make them permenantly attatched to my laptop as with the 2 sided tape will weakin after 6 months to a year or so.