What do you consider “powerful” as regards gaming? I have Verizon Fios (20mb/5mb), and the ActionTec MI424-V2 sending a signal to the WRT54G as a wireless bridge (with DD-WRT). When I run Speedtest.net on the wireless bridged clients, they get 18mb/4mb average. Not too shabby. LAN transfers are decent for the setup - about 2.5mB/s. I don’t game on the bridged clients (that’s just my Windows Home Server and family computer) so I can’t tell you what latency is like, but in short, the WRT54G is a very good platform for DD-WRT (I think it’s one of the most recommended, actually).
Hope that helps