I picked up a Pentax on ebay this year, and so far, it seems to be a great scope.
I started off getting a Gameseeker fromFox Optics (IIRC), and theyhintedthatthe Pentax Pioneer would be a better muzzleloaderscope. It's actually a Burris Fullfield II.

If you're want to stayaround $100-150,I'd suggesta Nikon Prostaff with BDC reticle.