For a similar setup, I have a Yamaha MX-35 power amp connected to the second set of outputs on my McCormack preamp. The Yamaha is very small and unobtrusive, has two sets of speakers terminals and plenty of power to drive small pairs of dining room and kitchen speakers. The best feature, though, is that there are gain controls on the front of the amp, making it very easy to balance the volume of the auxiliary speakers to the mains in the living room and a speaker on-off switch on the front if you want to listen just to the main system.
It might be difficult to find that amp used but I think there were several similar Yamaha models. It could be that th only advantage over your Harmon Kardon integrated is the unobtrusive look of the Yamaha.
My experience with auxiliary kitchen and dining room speakers is that almost anything decent will do since very little critical listening gets done there and it's hard to hear over the slicing and dicing, anyway.
It might be difficult to find that amp used but I think there were several similar Yamaha models. It could be that th only advantage over your Harmon Kardon integrated is the unobtrusive look of the Yamaha.
My experience with auxiliary kitchen and dining room speakers is that almost anything decent will do since very little critical listening gets done there and it's hard to hear over the slicing and dicing, anyway.