I'm an avid Tool fan and have been working towards those tones for a while. Had to get a T-40 to somewhat cop the Ric sound of Paul D'Amour. Justin Chancellor plays a Wal and i've tried many basses to get that tone. P's, J's, Rays, Spector, Warwick, Peavey, Ibby, Epiphone, Gibson....you name it.
So...IME/IMHO: Some sort of Ray variant seems to get the closest for me. They seem to have the right midrange complexity for the sound and you kinda get that aggressive sizzle that, I think, makes a Wal stand out. If you can find and install one of those filter preamps that i've heard people talk about, you're probably gonna get close enough.
Also, while not as close, a Warwick that has some big humbuckers seems to be the runner up with some careful EQ'ing.
Wisconsin Bassists Club #65