Have a look at what surfboard do i need in the sticky threads.
The sb5100 as far as i know is the same modem as a sb5100i.
The only difference is you will have to buy a 12v transformer for it.
The sb5100i has a transfomer that you can select the voltage.
If your excw then you will need any surfboard so long as it's got an e at the end.
I got sb5100e.
I think if i knew now what i didn't know then i would went staright for a sb4***e
Got one coming ,but i think it would have been a lot less hassle.
a transformer from maplins will cost about £7,add that to the cost and shipping and see of it's worth it?