Guest : Loose4Bruce, this is your lucky week.
I just happen to have a Yamaha RX-V2400 with a set of Athen AS-F2 towers and the AS-C1 center channel, and, all I have to say is that the sound is great! If you think that your Harmon Kardon is giving you crappy sound, go with the Yamaha. That YPAO that they have in there now does wonders for room acoustics! Also, if you want to see a really good review for the Athena's go to Stereophile.com and see what they have to say about them. Just type "Athena" in the search box and it will bring up the reivew for you. What Robert says about them holds pretty much water.
Trust me, you can't go wrong with this set-up.
The Athena's play loud and hard! Oh, and with the Yammy 2400...it too seems to lack in volume, until you start getting real close to that 0db level, then she just lets loose.