#1
I've got a couple questions about compression pedals. First off, are there any moderately cheap ones out there that don't add a ton of noise? Of course, I have a noise gate, but it's only a cheap one and with the compressor I tried, it didn't cut out all of it. I tried a Route 66 compressor/od pedal and it added a lot of noise. I would be using with distortion and thus, must be very quiet.

Secondly, I was told that this was the way to go to help me get better djent tones out of my amp. Would this do it at all? I realize that most of that type of tone has to do with technique and eq'ing, but I want to get it ALL there. I have a 10-band EQ pedal and an Ibanez TS-9 OD pedal, so I'm pretty much there, the thing is, I can't get a good clean tone right after a distorted tone without stepping all over the place. Would a compressor be what I'm looking for here?

I basically want to have a pedal that I can leave on and get both good cleans and good djenty distortion out of it while keeping the gain at a low setting. Not having tried many compressors, I need your help. Perhaps a clean boost is more what I need, or am I on the right track with a compression/sustain pedal?
#2
I have no idea if it's useful for djent, but as far as noise goes, compressor + distortion = tons of hiss. There's really no way around it. It's the nature of the device.

You can minimize noise by using a noise gate between the guitar and compressor and putting all your other effects after the comp, but even very good compressors add quite a bit of noise on heavy settings, and introducing distortion is only going to compound the issue.
#3
What a compressor does is to even out the dynamic range of the input. It brings the quieter notes up in volume, and pulls the louder notes down. This is why compressors are perceived to add noise to your signal. They don't really ADD the noise, they just bring the noise that is already present up in volume. The higher the compression, the more prominent the noise will be. You might want to try putting the compressor first in your chain, that way it amplifies as little noise as possible.

What do you not like about the tone that you're getting? Also, what kind of amp do you have? Tubes respond very differently than solid state amps when it comes to compression and overdrive, so it definitely will make a difference deciding what you need.