I've got the D-Link 604+ and have two PCs hard wired into it and a laptop connecting via wireless. I run all three on it into BT Openworld 512 ADSL; one of which is usually running AH, one operating in background running MS Office applications and monitoring two email accounts, and the laptop surfing the net generally (some games)
Unless there is a Big download taking place, there seems to be no drop off in performance across any of the other PCs, and certainly nothing that has effected playing AH (though the AH machine is hardwired and not running wireless).
The two hardwired machines are in the same room, the laptop can be anywhere in the house or garden - doesn't seem to have a problem anywhere. (60ft radius)
The only comment with the 604+ is that the manual is next to useless if you haven't got a clue about networking (which I didn't). The connections are simple enough, and provided you know how to configure the router (you can get that info from your ADSL providers site), then access to the net is very simple. The difficulties I had were all related to sharing drives etc. and in the end, I realised that I had to disable personal firewalls on the individual machines to get file sharing to work. Still very secure though, the firewall in the router itself keeps everything unwanted out.
Once configured it seems very reliable, running connected 24/7 with the only downtime caused by BT.