Brewer..."horrifically despicable"...I LOVE that phrase. That is a handy phrase I can use instead of the coarser "major suckage" I favor.
But, anyway, in answer to the original question about "needing" a bass amp. My philosophy is that if you are committed to playing bass and making it be all that it can be, then make the committment to buy what is needed to achieve that goal. Even a small pratcice amp with one ten inch speaker will do wonders to your ears when learning what you can make that bass do.
It also means buying a good quality cable, a comfortable strap, decent strings, and I'd add a tuner and an electronic metronome or basic drum machine too. Just those little fundamental accessories will make a difference. By trying to see how little you can spend or buy, I think you cheat yourself and deprive yourself of the entire bass experience. If you are committed to playing bass...that is. If the bass is just background for a guitar recording or whatever, well, then just use what you have. But the key word here is "committment." How committed are you to bass guitar? Having a corner cutting mentality won't give you all you can get. Jason Oldsted