Bought a D-Link DIR-655 Extreme N Wireless Router - Need advice

Hi,

I bought a D-Link DIR-655 Extreme N Wireless Router, and would really appreciate some advice. To explain, I have one computer that is wired to the router, and I have three or four laptops in the house, all with built-in wireless (G). The wired desktop is a gaming PC, so I think I'd like to have one channel for that, and another for all other traffic. Would you all recommend buying new wireless-n adapters? If so, would you recommend USB adapters or wireless network card adapters? Should I buy only D-Link, since that's what my router is? Will I get better reception/speed without buying them? Right now, performance can be bad, and reception is worse.

Finally, can someone please recommend a tool I can use to do some sort of baseline testing on network performance, so that I can run it before and after installing the router? I'm installing it later tonight, so hoping someone might be able to give me some ideas.

Thanks so much!
Steve