bass effects
 

Im looking for a good bass rack mount multu effects, the only one i know of is a line6 that they dont make anymore. Anyone got suggestions?

Why are you specifically looking for rack mount unit?

Here's the quickest one I could find:
Behringer Bass V Amp Pro Multi Effects Processor at AmericanMusical.com

Behringer isn't exactly top of the pile but they're known for providing quality at affordable prices. Ultimately you get what you pay for.

On a related note, does anybody really like to play with heavy FX on their bass? Every time I've tried to incorporate them I end up just messing with my basic lows mids and highs to achieve the sound I want. I don't know, I guess I feel like it takes the..."grooviness".. Out of the instrument.

Yeah. The bass plays such a fundamental (no pun intended) role in most music that effects take the zing out of the proceedings, excepting if you make it the primary instrument of the song.

I've yet to find a really good way of incorporating any sort of heavy effect on a bassline.

I will say that one effect I absolutely love on a bass guitar is tremolo. Pluck a few long notes with that and you've got a pretty cool, almost eerie vibe going.

Yeah, I've known a few people who would tweak the sound significantly and done so as well. The most basic purpose is to emulate a keyboard / synth tone.

Generally speaking you're right though, it does take away from the grooviness but at the same time depending on the style you're trying to perform you might want a more particular thump as opposed to a groove. Like if you're trying to do a live performance of jungle / rave style music - or a Squarepusher cover.

Or, there's also the TOOL method of playing bass which revolves around running a wet/dry setup through a pair of amps so that you never lose the grooviness of the natural bass tone but then have an equal layer of manipulated and modified tones colouring the overall scope of the instrument's role within the ensemble.

Add in a bunch of fuzz, a teeny tiny bit of flanger, and you've got THE 'dubstep' sound.

^Thats interesting you mention that, as I do something similar in recordings all the time. I'll take a guitar riff, baseline, even a drum beat, and add some post-production FX to it. Sometimes it'll sound really wild, so I'll double it up and add the "natural" track under it. It gives the sound an edginess that usually sounds pretty cool.

^ From what I understand that's actually a quasi-standard practice. If you pay close attention in the majority of classic rock tunes even though there's clearly an electric guitar in the forefront there's -usually- an acoustic guitar doubling the rhythm hidden in the mix.

It's a way of fooling the listener into thinking they're hearing something really wild and off the wall while still coddling their subconscious listening with traditional sounds.

You're right, it's actually very common to stack a few layers of instruments/FX behind the lead riff/line/beat. It's actually done with vocals a lot, too.