system for a 12 year old

I'm going to assemble my 12 year old son's first system.

OK, so he doesn't know the difference between a woofer and a tweeter. Still, there are decisions to be made....so I request your comments and observations.

I bought a vintage yamaha CR-420 receiver for a pittance on ebay and plan to build from there. I have not received the Yamaha yet, but when I do I will either assign it direct to my son's new system or replace my vintage NAD 7020 receiver in my 2 channel a/v system and donate the NAD to my son instead.

Next, my plan is to add a pair of Klipsch RB-51 monitor series bookshelf speakers, which I've heard at BEst Buy and was very impressed with for the price. This will settle my yearning to gain exposure to a pair of horn based speakers at low cost and risk initially. I can then either dedicate the Klipsch's to my son's system with the Yamaha or NAD or replace my Triangle Titus's or Ohm L's and moved one of these to my son's system which will go in his modest sized bedroom.

Not sure which way this will pan out yet at this point, but I welcome any comments or observations.

Thanks.