Way to go! You've got a lucky boy with a great system. I still have my full NHT 5.1 HT set up (Twos, Ones & center) from my HT days and love them. I've currently got the SuperOnes doing 2 channel HT duty in the living room...mostly for my 3 1/2 year old boy.
I use a Marantz SR 19 EX receiver. I've had the NHTs and Marantz for years and they get used regulary and I never get anything but satisfying performance. If your "son" gets the upgrade bug try out a Marantz receiver for some synergy with the NHTs.