You have a pretty good size network with 15 computers, but if your going to grow down the line, a PIX might do you well. I think it depends on how comfortable you are running a PIX, or if you just want to stick with GUI interface on a standard router.
I came across a firmware which basically turns a standard router into a more professional type router, as far as features. Its called DD-WRT which is owned by GNU.
Source Link:
www.dd-wrt.com/dd-wrtv2/ddwrt.php
You will be using a Linksys WRT54GL Wireless G router. You will then download the firmware of the DD-WRT and flash the router. I have currently implemented this router in my network, and I must say there are quite a bit of options. I would recommend looking into this a bit more and see if its something your looking for.
I also have a PIX firewall, which I am currently learning to use. I have a PIX501.
Cheers,
ZiPPy
