Thanks for all the replies, folks!
Four comments/clarifications:
To the question posed, I think a high end bass will improve your playing, because it will magnify any signs of poor technique and force you to correct bad habits. But depending on your style of music, that may not be a needed or even wanted thing
I personally prefer (and am working on) jazz, progressive, avant-garde styles (probably stemming from my classical background), but I'm still very much in love with blues, rock, even some metal. I'm kind of a musical universalist in this sense...I enjoy at least a part of most everything that comes my way. With this in mind I feel it may be good to have an easily adaptable instrument in the future...
If you can't play, you can't play.
That said, a better instrument *should* be easier to play. A cheap instrument will often require you to "Fight" it to do what you want - and that's no good.
The key concept here is ease of play - appearance and tone mean nothing if you can't play the thing, right?
I am no virtuosic player as of yet (having only seriously practiced ["seriously" meaning consistent 4-7 hour sessions] for a couple months), but I'm ultimately aiming for as fluid and spotless a technique as possible. That being said, I don't feel that I'm so bad of a player that the bass has nothing to do with the problem. Having already played a string instrument, bass comes pretty naturally and simply to me. Maybe I'm not good enough to overcome the bass's limitations yet, but...eh, as it is, more practice will probably solve a lot of things. It's just frustrating not being able to even try certain things because your sound is abominable.
However, I agree with others, a poor set up on a great instrument will sound and feel worse then a great set up on a mediocre instrument. Also, at some point, it does all come down to you. Don't expect better slap tones if you can't slap, don't expect the miracle of Jamerson to come out of your fingers just because you have a '62 P.
Point taken. Once again, I'm not as well-rounded a player as I hope to be eventually, but I'm not so terrible of a player that these concepts are way out of my league. The way it is right now, I can't bring myself to practice slap because the resulting sound is too bad (even though doing the same thing on that other, better bass I mentioned previously made a nice, compact, appropriate sound), so currently, I'm going nowhere in that area.
There is also that setups vary depending on playing style. My Sterling has a medium to low action for fingerstyle and pick. My magnum has quite a bit of relief to the neck for playing with a pick very hard without bottoming out on the frets. Likewise for slap you want a different setup.
Apologies if this is a ******** question, but does this mean I need to change my setup for each playing style to get the best sound? What if I want to switch between various styles within the context of one song, i.e., fingerstyle to a slap section, then back to fingerstyle, then a tapping section, etc.? (obviously this is a hypothetical situation and most likely rare, but still...for the sake of knowledge and experience...)