does your mixer have a pad switch on it? I have a bunch of mics, and I get a little hisss on all of them, but if you turn the pad on, there will be little or no hiss, in my case no hiss at all. Look for an outboard pre amp, like the dmp3( a lot of people arpund here swear by it) and ditch the compressor. this is just my opinion BTW. Most say no compression on the way in, record it as clean as possible and tweak all you want once its recorded.
I have a presonus bluetube dsp and I really like it and it suits me well. The dmp3 is regarded as a very good clean pre so I would consider that first. The pre amps on behringers tend to suck.
all my opinion mind you, I am learning day by day myself.