Bazooka

I have recently purchased RF82, RC62, RS62 and RW12d mated to Yamaha RX 861. I listened to the same system at the dealer using the same CD (Linkin Park - Minutes to Midnight, Eric Clapton/JJ Cale and a few others) and it sounded great. Now at home (I have a smallish room, prob 4m x 7m) listening to the same CD I can hear some jarring/distortion at high frequency, although still sounds pretty good. What could be reasons for this? (room size, newness of speakers..)