if i tap a peak lead and vu meter to my main output(soundcard)
Will my audio degrade?
or should i put something

 

The Peak LED circuit may have a detrimental effect (non-linear diode and cap to 0V) so take its input from the the output of OP2 to avoid loading the output to the soundcard.

 

You can using the comparator as LM393 to setup the voltage to do the voltage comparator that you want to detect, and you can also using ne555 to do the monostable circuit to keeping the peak state with led to show the state how long you like, or you want to have a led fade out effect.

 

I agree with Scott, a comparator is the way to go, since it usually has a high impedance input.