Ford F150 - Need higher output alt?

I was expecting the power sags with my under drive pulleys. They arent causing me any problems since its full charge at about 1k rpms. My only concern is in the near future I'll be adding some offroad KCs and a stereo system with amp. My truck idles pretty low, around 600 rpms so would getting a higher output alt be beneficial in this case? Or is there any easier way to go around it?

Typically, a HO alt puts out less at low RPMs than a smaller alt. So if your primary concern is idle performance, stick with what you've got.

But there are several good discussions about upgrading to a 3G ('92-96 style) alt on FSB, so spend some time reading them there. That site has an excellent search function.