how far away is the router from the modem? you could use the router as a signal repeater from the wireless signal from the router/modem combo and you wouldn't have to buy any more hardware. you could also buy a directional antenna, or build one yourself with tinfoil and cardboard. If neither of those works then i suppose you could buy a cheap DDWRT compatible router and set it to repeat your routers signal somewhere in between your bedroom and the router.
__________________  |