Hi Josh,
Sorry to hear that you haven't found the right bass....your walnut MTD635 is great by the way..
Setup is a highly personal thing...but a few years ago I broke out of this low action obsession, decided to get my basses sounding good by raising the action quite dramatically and then figured how to play them. It's the best thing I ever did...I occasionally sound quite good these days! Here's my idol's view on the subject (John Patitucci from his website) who has his action set quite high on his basses which results (to my ears at least) in a lovely pure hi-fi sound...thought I'd share the benefit of his experience.
STRING HEIGHT: "For both acoustic and electric bass, you need enough clearance between the string and fingerboard so you can pull a sound out of your bass. If the string is too low and right on top of the fingerboard (or frets on the electric), your dynamic range between your softest and loudest sounds will be smaller. For the acoustic bass, the top of the bass won't vibrate as much and you won't be generating as much sound. You won't get as thick a sound and you may get noise when you dig in and have to play stronger. For electric bass, again, I feel that the instrument must vibrate well, even though it is most often a solid piece of wood and there are pickups involved. It is still an instrument that is initially acoustic. So, you still need some room between the string and the fingerboard. It seems to me that many players sacrifice sound on both acoustic and electric, opting for convenience and greater ease of playing. You have to find the balance between ease of playing and getting a nice full sound with ample dynamic range. I have experimented a lot over the years and have my action on both instruments at a moderate place. I seem to have my action on electric higher than many players and more like my hero - James Jamerson (who played both acoustic and electric). This is not a value judgment, but a subjective preference."
Alan