The second zone (and the tape and video record outputs) only works with stereo analog inputs. As such, the second zone only works if the selected source is connected with analog cables. Also, the second zone has separate input and volume controls, so you will need to operate it separately. If all nine speakers are in the same space, you may run into problems getting the levels matched up.
If the second set of speakers are remote and you don't mind hooking up stereo analog cables for the sources you want to listen to in that location, then the answer is "yes" - this is exactly what the second zone is intended for.
As for a good, inexpensive two-channel amp, what speakers will you be driving? Depending on efficiency of those speakers and desired volume levels, there may be some very economical solutions along the lines of the little Sonic Impact T-Amp, but that's a very low power product. For higher volume levels or low efficiency speakers, you may want to look at Audiogon for used amps.