I'd get the Linksys WRT54GS with the G card that has speedbooster. I bought both for under 200 dollars and didn't have any trouble.
Some people say just get the WRT54G instead of the GS but I didn't have any trouble with mine. It does B or G or mixed, has a lot of options too. I got 2500 down/233 and 4,200/499 when I tested it. It is fast.
forgot about gigabit