I personally wouldn't buy a used router, but thats just me. What exactly is "too expensive"? I have a Cisco (Linksys) Dual Band Wireless-N ---
This one.
I got it for about seventy bucks in store, with a coupon from my reward zone card. It's a great router, and hasn't given me any troubles. We have two PS3s, three xboxs, a Wii, three laptops, two ipads, my cell phone, two blu ray players, two desktops, and two TVs (all that I can recall at the moment) that are linked up to it. Not necessarily at the same time, but it's a safe bet that at least four devices are using it at once at any given time.
I haven't experienced any lag, or dropped connections with it. It works upstairs, and downstairs with only one dead spot which is in the back storage room, where our furnace, and water heater are located.
In my opinion, this will suit you perfectly in case you do want to expand at a later date, and for now it will do you wonders.
Just my
