Router Change

No. If all your wireless clients are G, they can not connect faster than 54Mbps, no matter what the router is.The only exception to that would be some of the Pre-N proprietary standards that were out, but you won't find that on new routers today.You could buy wireless AC adapters to go along with the router, but you would need one for every client. How many computers are we talking?

5 wireless, 1 wired

Ouch, you would spend more on adapters then the router. I wouldn't bother upgrading the router.

Thanks.  Probably could save if I lowered my speed too, since not benefiting from it.

Yea, if I had a better answer for you I would give it, but having all wireless G computers creates a impassible bottleneck. A new router "might" increase the range of G, and thus possible increase your speeds, but you probably won't see more than 24-26Mbps, since 54Mbps is just the hypothetical limit. There are other options like MoCA or powerline, but you would still need to buy multiple adapters for each computer for that too. The cheapest way would be to run ethernet, but I know that's easier said then done.