I would have to say with everything you want to do to your AK, the stock, scope mount, etc....you would be better off buying the AR to start with. The DPMS Sportical has been selling for 800.00 on gunbroker and other places. While that is 230 higher than the Ak you mentioned buy the time you added the mods to your AK you would have been better off with the AR.
Tapco makes good quality goods and everything I have heard about their customer service has been good as well. When it comes to a scope mount ideally you want the mount and the barrel to be mounted to the same piece of steel so a receiver mount would be best.