like it was said before, i would not change timing without changing cams and even then i would not do it with out the help of a dyno, so you can see what you are doing
If i were you you i would buy muffler you like and then take it to a muffler shop and have them build it custom with 2in. pipe. I did mine that way and it came out with a good tone, that does not sound like a bumble bee on crack.
I have a 95 civic with a d16z6 v-tech motor and cannot decide whether to boost the crap out of it or just do a swap. I have heard good things about both, but just can not decide