Sorry, a cab is the cabinet which contains the speaker. If you look at a normal hifi speaker you usually see a big cone and a small cone. The big cone is good for low frequencies while the small cone (usually called a tweeter) handles the high frequencies. You need an amp to drive these speakers.
A horn is similar to a tweeter but handles mid/high freq through a horn lol.
But let us forget about all this. We got a few threads about affordable portable/mini amps. Hope this helps!