I heard that I can get some good power out of the underdrive pullys in my LS1. But I also know that I was a large power pull from my stereo. Should I buy pullys?? What ones? Should I get an overdrive pully for my altenator??

 

i dont think the pulley even with an alt pulley is for you..
too much stereo..

 

I have a little bit of stereo stuff in my car (just a 250 watt amp driving one 12" sub - no capacitor) and I have a crank underdrive pulley. The power gain was evident from the moment I installed it, definitely worth it. The only time I notice any slowing of accessories is at idle... the lights will be a little bit dim, or they'll dim on the beat of the music, and the turn signals will blink slowly, but at any RPMs above idle, it's completely normal.
I think when I eventually get more stereo equipment (more wattage) I'll get a capacitor, and an alternator overdrive pulley.
In your case, I think with like a 1.5 farad capacitor and the alternator overdrive pulley, I think you would be ok with the crank underdrive pulley.

 

What pulley set did you buy?

 

I have just a ASP crank underdrive pulley, prolly the most popular pulley out there for the LS1.