suggestion on new exhaust

[blind34_1]

I need opinions. My car (90 civic si hatch, 1.6 sohc) needs new exhaust badly. Questions are:

Will headers sound like crap on my car? Dont headers require two exhaust pipes to acheive the purpose of headers? do I not understand what headers are? If not, what brands are good?

Can someone define what a cat-back exhaust is? I just dont know.

I had a new "performance" muffler and chrome tipped pipes put on a while back. Can I still use these parts if I were to get a new system (headers, cat-back, new piping, whatever) or would that not be a good idea?

Is more restriction good or bad? I dont know the diameter of my current pipes, but if I increased the size, does performance increase?

Anything else I'll need to consider...?

thanks guys