I moved away from a Netgear wifi-router-firewall, replacing it with a Linksys WRT54GL.
Like you I found the Netgear was dropping out frequently, requiring regular reboots.
I have had no such problems with the Linksys. At all.
I'm on cable, but I'm sure there's an appropriate ADSL Linksys device.
You don't mention what the wifi cards are in the PCs you have, but G is backwards compatible with B. Wireless N is available, and such devices also work with B and G. The speed advantages of 802.11n are only available with compliant cards, of course.
SD