As you know Cisco bought LinkSys, but LinkSys is still LinkSys and you get what you pay for. I don't believe Cisco makes the 501 PIX anymore, they may not even make the 506. Of course, neither of these are wireless.
You don't necessarily need a router in a network configuration if you have only one segment. We have only:
Cable --> Pix 501 Firewall --> Switch --> Server and clients.
You will get many answers as there are many good routers/firewalls, but I would concentrate on a good firewall as the LinkSys above certainly is not in my opinion.
I would actually call Cisco 877-235-5477 and tell them what you are looking for and how much you are willing to spend. I am sure they will steer you in the right direction. You can always purchase the device online much cheaper. But, if it is a fairly pricey one and they give you one year's support, I would grab that.
