[jem]

Well wireless does introduce a bit of overhead but nothing like they drop you are seeing. When you say it works at 18 Mb/s on a wired connection, is that with the PC plugged directly into the VM cable modem or plugged into one of the LAN ports on the router. The reason I ask is that the speed sounds just like I would expect if the WAN port on the router was running at 10 Mb/s in half-duplex - but if that is the case then you should see the same speed with a PC plugged into the LAN ports.

Either way I'd investigate a bit further before committing to getting another router, I suppose you don't have any neighbours etc. connecting to your wireless system, do you?