Well, my first suggestion is that you get a good switch to compliment your router so that you don't have to use your laptop as a bridge. If you're playing FPS, then using your laptop as a bridge is always gonna leave you a half step behind everyone else.
The difference between the WRT54G and the WRT54GL is the amount of flash memory that they have. The WRT54GL has twice the amount of flash memory which is what the firmware is stored on. This allows for greater flexibility if you want to run third party firmware. I am personally a fan of Tomato firmware. Runs very well on the WRT54GL, and gives you a lot of additional features and control over the router. You can adjust the wireless signal strength with Tomato to 3 to 4 times what Linksys sets the signal strength by default.
I personally find that the WRT54GL is worth the extra $10-$15.
If you want to go a little higher end, the D-Link DIR-655 is getting some pretty good reviews on Newegg, and is on sale at $99.99 with free shipping. You'll be a whole penny under budget!
http://www.newegg.com/Product/Product.aspx?Item=N82E16833127215