I have played the swap out PU game on many basses over the years. IMO I don't think that it really changes the sound all that much. I think you can affect small tonal responses but my experience is that if you are looking for more than a small shift in sound, you will need to find another instrument. It is a fun journey tho. I still take it myself...
p.s. I also feel that expensive does not equal better. I have gotten some of my best recorded tones from a cheap microphonic, noisy Vox Apollo IV pickup.