I have a cheap Squier P Bass going through an Ampeg BA112. I just changes the stock pickups out for a set of Mighty Mites. The difference in response is considerable. The MM's are somewhat hotter than the stockers. Tone wise, at lower volumes like in a church, they deliver a nice, deep, powerful sound, even through the 112. At higher volumes they will overdrive the amp nicely, if I want them to.
I spent $30 on them and feel pretty good about it.
My set up is low budget all the way. Guitar = $100, Amp = 200, Pup's = $30, Flatwound strings = $30.
Best thing I did to the guitar was to re-work the nut, set the neck angle, set the action and put the flat wounds on it. It makes the sound that I like.