These are intended to fit on the power feed to your CB, which has a 4W output, so the 10A one should be plenty. As Western says , it is always better to stop the interference at source (just look at an FFR machine) so it doesn't radiate using tha wiring as an aerial.
The main sources on a car are the ignition (if fitted), alternator / dynamo and the wiper and washer motors. Distributor condensors come in handy cans with wire tails, and can be connected across live (12V) and earth as close as possible to the source, and make a world of difference (I can actually listen to 198 long wave (AM) with the engine on!). You can get purpose-made suppressors, but all they are is a rugged capacitor with a mounting tab (can't find any on eBlag at the moment).