would upgrading my alternator to suffice my stereo's needs take away horses?

 

The alternator itself would not matter, but more so the pulley on the alt. If it's a good bit bigger than the stock pulley, then you'll be creating more accesory drag which can cost a couple of HP.

 

you may be able to save a couple of dollars and buy an overdrive alternator pully, ive seen these at some places (could have been a sponsor) and it shouldturn up the juice just a little

 

Alternators are pretty efficient and don't apply
much drag at all if you're not drawing current.
Run the stereo at "11", though, <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" /> and you'll
probably lose about 1 HP.

Some of the highest-current alternators are a
less efficient design but again this only
matters when you apply a substantial electrical
load. I bet housekeeping electric load is only
a few hundred watts (1/2 HP at the shaft or so).