First off don't fall for the hype on the range booster, it doesn't work. I like the linksys with removable external antennae. You can also consider disabling the internal laptop wifi adapter and get the Engenius/Senao USB or PCMCIA Wireless adapter which have lots of power and also external antenna connector. Also to solve (or at least help) the upstairs/downstairs problem lay one of the antennae horizontal to change the radiation pattern to vertical as opposed to horizontal. You could also consider putting the router in the basement with you.
HARDWARE: Fujitsu Stylistic ST5111w/WiFi and dock, internal Hitachi 500G HD, external 1TB HD, Sierra Wireless Aircard 550, DVD-RW, BoomzBox HD radio, XM Commander, Delorme GPS, Saitek X-52 Pro joystick, BluSoleil Bluetooth, TPMS, FB, Elm327