I voted bass. You might be in a situation where you don't need an amp. (Backline is furnished----Studio work with a DI---etc.)
I thought about it, was about to put bass, but I feel that in a situation, Id rather have a crappy bass (no cheaper than $200 new... come on now...) and a rackmounted setup with 500 watts and equalizers and compressers yada yada. My warwick FNA sounds bearable at best through my 10 watt crate combo, but a Ibanez GIO through my 1100 watt hartke half stack with filled 6 space rack?? much better
GEE how many times do I have to type this in 24 hours? BASS and CABS, BASS AND CABS, BASS AND CABS. BOB and XXXX
Hmmm...without an instrument, the amp's useless, and without an amp, the instrument can't be heard. So I think the most important thing is the player.
touch and strings... second is bass.. (assuming you're playing live - you'd be DI for any realistic size venue).
In terms of money spent with tone being the goal; I spend more on a cabs and amps and less on basses.
+1 on amp, I'd play pretty much any bass as long as I had a nice versatile amp, that and a great cab.