I'd buy what the ISP is recommending.

I have Comcast cable internet. They had a list of recommended modems to buy. I made sure to buy one from the list.

Thanks for the response, IEEE448.  Much appreciated.  I'd normally do that, but the SpeedTouch 546 they are recommending appears to be 802.11g technology and isn't even for sale anywhere else as it's long been superseded. 

I have a Dell Wireless 1505 Draft 802.11n WLAN Mini Card - not sure if that makes any difference.

I'm really keen to take advantage of faster download and/or streaming speeds.

Lulu

Looks like both devices are modem+router in one.

I had Verizon DSL where the modem and router was one unit. I put it in bridge mode and used my own router. Perhaps something can be done for your situation.