I had a bad coil as well, but I was running Jseabert'* stockers when the MSD'* came in, so I had a good comparison. It was noticeable. I'm betting that'* why the 'seat of the pants dyno' is telling you.
Coils should run about $120 for all three, plus wires (about $50 more). I wouldn't waste my time on the MSD coils without putting a good set of Taylors or MSD wires on there at the same time.
Jegs for the coils, you need the 8224'*, and www.grandprixstore.com
for the best price on the Taylor Spiro-Pro wires that I've ever seen.