Ok, there are tons of possibilities for good bass amps. If you want something to carry around to anywhere you go, I recommend the micro cube. It's tiny but potent, and although it is a guitar amp bass comes through well on it. For playing live, the Fender BASSMAN '59 is outstanding for a powerful sound. And for practicing, recording, or just jamming, the Fender BRONCO 40 is your best bet. It costs about 200€ in Europe, in the US probably around 300$, maybe less? Anyway, these are, in my experience, some of the best amps.