It depends on how big of a network you plan on having. First and foremost I am not aware of a third-party firmware for your model number. If you want to mess with the firmware you are better off going to Buy.com and picking up a Linksys WRT54GL. Not the L. The version 5 WRT54G routers do NOT use Linux and therefore are useless with OpenWRT, Sveasoft and DD-WRT. There are other models besides Linksys to use as well.
Alas, if you are stuck with the SRX you might want to give a canned solution a shot rather than build it yourself. m0n0wall
is one of the easiest but I am not sure what type of authentication it uses if any. It might just be a captive portal and if a CP is all you are looking for you can't beat the Sputnik firmware
upgrade. It is easy to setup but again you will have to get a different router.
If you have some patience and skills you can setup NoCat
. Rob Flickenger, author of Building Community Wireless Networks, co-wrote this software. It doesn't take a whole lot to setup but newbs might be wise to play in third-party firmware land.
There are a lot of choices out there but all take a little patience and lost of reading.