I use a LinkSys WRT54G wireless router in conjunction with my Apple Airport Extreme card for my iBook. Using 802.11g I get pretty decent signals all around my house. I have the router on the second floor, and get 3-4 bars anywhere on the second floor or the first floor, though I haven't tried in the basement yet.
In fact, I have a TV on between me and the router, a wall behind the TV, as well as another computer inches from the router, and I have a full signal bar (4 bars) on my Airport Extreme. 54Mbps is my current speed.
If you're only on 802.11b then the max speed you can get is 11 Mbps, so your speed will be adversely affected by other factors, like Huggy said.
My advise, if you aren't on 802.11g, is to go for that, or just hook up through Ethernet when you play to keep your speeds constant.