wireless cable router advice!

Hi, we've just had telewest install a cable modem at our house but
unfortunately I didn't realise that ADSL routers weren't compatible
with cable modems. The DG835GT router I bought just about manages to
reach through the house (reaching my WG111T USB stick). We need to get
a new cable modem with a better range. I was considering the WPN834 for
its greater range. My two questions are
1. Is the WPN834 compatible with telewest modems (via ethernet
connection)?
2. Would the laptops and USB wireless sticks throughout the house pick
up the newer router signal? For example, would I have to change my
stick to the WPN111?

any help would be greatly appreciated
thanks

Owen