Wireless (wifi) speed isn't down to what speed the broadband is - it's to do with the speed of the hardware. Wireless only really comes in three formats for the home user (there are variations, but three are the most common), and these are all based on the 802.11 protocol. 802.11b, 802.11g, and the newest, and still not a strict protocol is 802.11n. .11b transfers at upto 11Mbps, .11g upto 54g, and .11n can acheive speeds upto 300Mbps (country code dependant)

the good news is, even if you don't know what speed your router can run at, they are backwards compatible. IE, G routers can work with B cards. (N can also work with G + B, but only if the frequency is set to 2.4Ghz and not 5Ghz)

Some routers, like the Netgear "Super G" routers use two channels to send two G signals to create a 108Mbps signal....

If you can post the model number of the router someone can tell you what adapter to get.

My laptop has an internal card and is only B speed, so only gets 11Mbps but is fine for surfing and even the odd programme download, and manages okay streaming music and video... My router is a Netgear that is B+G compatible (and 108Mbps Super-G) so works with my laptop fine....