I used a cheap Amazon part that had good reviews. But since the misfire is on all cylinders, I wouldn't think that one bad coil could cause that. I could be wrong, of course.
'04 GTP Comp-G - 14.871 @ 93.30 (6600 ft DA) - 3.6 MPS, SD headers w/ high-flow cat, Gutted stock airbox, Transgo shift kit, AL 104s, 180 tstat, GMPP front sway bar, poly control arm bushings, Tune by Dyno Brian