What is your basis for saying that? See my earlier post - it would appear the router is many times faster than his internet coming in. How can the router be 'the weak link'?
The WRT-54G v1 model is very old, and scored near the bottom of the results posted at
smallnetbuilder. I saw that model last night, but it is not there now.
The WRT54G2 v1 model is newer, but it could be a 2008 model. I am ok with that for now, but a firmware update could eliminate certain problems the OP is having.
The reason I referred to 2 different models is that the OP mentions a Linksys WRT5462 v1 model. I think we really need to clarify the specific model, the firmware, and the manufactured date. Newer routers have so many features, I personally think a new one is in order. However, that is just me.
Over the past decade, I've probably worked with a few dozen wireless router installs. There are many nuances to be considered.
In the OP's case, we don't know the advertised bandwidth the ISP is supposed to provide. We don't know what actual speedtest shows on a wired computer, or wireless one. We don't know what all the devices are, nor there wireless requests. We don't know of any interference in the environment. And we don't know the specific router model or its firmware.
Now we get to what these dang users are trying to accomplish on the internet.
I don't understand how you are so sure the router is not the weak link. The smallnetbuilder page shows that there is a wide divergence of performance among routers. There could be a specific performance problem in that v1 model of WRT54G2. I see there are hardware models 1.0, 1.3, and 1.5. No firmware updates for 1.0 or 1.3 hardware. Now that I dug deeper, I am convinced the OP will see better results with a newer router.
Rather than finding a single bottleneck, I consider all of the potential failure points (bottlenecks, if you will). Experience tells me that there is usually an interaction of more than one failure point. For instance, the older router is a weak link in that it does not have newer features which address streaming. However, some of the devices may be having problems with the security on the router. And I don't assume that the ISP is delivering high-speed until I test it.
There are many things that could be discussed, but I'd buy a router to replace the 2008 model, and move on from there.