My priorities are generally the same as @BigRedX - generally I'm attracted to unusual but attractive basses, although I do have an Ibanez SRF705 which I find somewhat insipid styling wise but does have rather good fretless sounds, and a Variax 705 which follows Fender styling cues but, well, it's a Variax. The bass must be playable (for me, slim and shallow neck, not too concerned about string spacing). I have upgraded pickups and/or preamps on some basses when I've decided that the sound isn't good enough (generally when it's too thin).