What router to buy?

Currently, I have SBC Yahoo DSL Elite internet connectivity with up to 6.0 MBps downstream and 768 kbps upstream. My setup right now is just an ethernet cable connected directly to my pc from the Speedstream modem. I also have an Xbox 360 I would like to connect to the internet, and instead of buying the overpriced Xbox 360 adaptor, I am going to buy the Linksys WGA54G Wireless-G Gaming Adapter.
http://www.amazon.com/gp/product/B0...=1789&creative=390957&creativeASIN=B00009X6DT

What kind of wireless router would be best for me? Also, whats the difference between wireless b, wireless g, wireless a, and wireless a/g? Looking to spend no more than $80 if possible.

 

Seems I found a chart comparing the wireless standards available.
http://images.amazon.com/images/G/01/electronics/detail-page/linksys_comparison.jpg
Would shelling out the extra cash for a wireless g router with srx be worth it in the long run?

 

Well, a heads up, I bought the Wireless G router with SRX, and I have done the following to try and secure it:

Changed the SSID
Added a pw for access to the router
Disabled Wireless SSID Broadcast
Used WPA-PSK security with a randomly genereated 50 digit pw with AES as the WPA algorithm
Enabled the wireless MAC filter
Disabled remote management
Disabled UPnP

Anything I might have missed? Or is my router as secure as possible?