As a follow-up to my original post concerning powering the second zone I'll offer what I finally did. I found (online @ J&R Music) a reasonably priced ($130 +s&h) 50 watt power amp. The brand is "AudioSource" and it goes by "Amp 100".

In addition to being more than powerful for a secondary zone in my kitchen and deck, it has a neat auto shutdown feature. It will turn off if it doesn't see any signal coming into it's line 1 input. (It has 2 line level inputs). It also has the capability for "A or B" speakers. It measures 3" H x 16.5" W x 9.25" D, so it fits into my rack nicely.