i never had exhaust without headers on this car now... but i had a hooker aerochamber kit on my old 93 with stock manifolds and ypipe for a while before putting headers on it and i was pleased... but its a huge muffler... just warning you if you go that route.... and the tips are not very eye pleasing to me... but you can always change those... depending on how much money you want to spend... the hooker is cheap... so is magnaflow... borla and corsa are up there... i run GMMG as you know and i love it... but thats up ther ein price too and i have no idea what it will sound like with out headers... might be very raspy and backfirealot with stock manifolds... here a site i used to listen to exhausts... its mainly ls1 stuff but there is a good amount of lt1 stuff too...
http://www.ls1sounds.com/ ....and youtube is also your freind... there is alot of crap on there...