Klipsch, Mordaunt Short, and KEF all make nice speakers, but you seem to have either their older or smaller models. Given that you have the Onkyo 805, there is plenty of room for improvement if you upgrade at least some of your speakers. There are many options, for examples:
1. If you are happy with 5.1, you only have to add one amp. For example, you can upgrade the KG3.5 to one of the Klipsch reference models, use zone 2 to power the KG3.5, and then use the Kenwood to power your zone 3 Mordaunt Short or the KEF whichever one you like better. I am assuming your Kenwood is an integrated amplifier, and therefore has its own volume control. If not, then you have to use the Onkyo to control the volume.
2. If you plan on listening to 7.1 in you main zone, then you may need two amps, one for zone 2 and one for zone 3. Or if you don't listen to zone 2 and 3 at the same time then you have the option to use a speaker selector and save one amp.
Unless you are planning on doing critical listening in zone 2 and/or 3, I would just get one or two cheap integrated amps or receivers, and feed them off the 805.
Again, the 805 has enough power for your highly efficient Klipsch speakers. Adding an amp for the front speakers surely can't hurt, but you will most likely do better by upgrading the speakers. If you really want to add an amp to your capable 805, then you should not consider anything rated for less than 300 WPC, otherwise there is no point. As for matching, I don't think you have to worry about it. The preouts on the 805 can be used to drive any standard power amps on the market.