I have the complete KSF package with 10.5's as my mains, C5 as the center, the S5's for surrounds, and the KSF 12 for my HT setup. As most speaker junkies I have often thought about upgrading, but as far as HT, this Synergy package has been outstanding. I originally started with the 8.5's but upgraded to the 10.5's when the chance arose. Keep an eye out because I have seen these speakers pop up for sale at reasonable prices. A C5 center went for $160 on ebay just last week.
If you could piece together a HT with the KSF series your son would be in high cotton. If I see anything come up for sale I will give you a shout.
Good Luck.