That's right. If you can find out what speed your connection is, you'll know for sure. The cards are cheap, but it would be a shame to spend it when it's not needed!
Even if you are surpassing 10Mb, you can pick up second hand 100mb cards for about 50p (around $1) these days.
Carlsberg don't run I.T departments, but if they did they'd probably be more fun.