outdoor speaker help

I am a newbie here so bear with me if this has been asked before. I recently bought a house where the previous home owner had it wired for his home theater and speakers in the kitchen and outside. he left me the wall mounted Axiom speakers and the (slightly weathered) speakers by the hot tub. the outdoor speaker areas each have a volume control (one for pool and one for hot tub on deck) I still need to buy the speakers for the pool area as the previous owner took his with him. The wire is already run. I am thinking of just getting 2 Infinity 100 watt Rock speakers to blend in with the landscaping.

I went out and bought an Onkyo 7.2 channel 770 watt receiver that has 2 zones. It is tied into everything (except the pool area until I get speakers).

The problem is that zone 2 is playing even with the volume up pretty high the outdoor speaker is not very loud (yes the volume control is up all the way). I even bypassed the volume controller and it made no difference. Meanwhile the kitchen (also zone 2) was REALLY loud.

I have already spent a small fortune (for me) on stuff and want to make sure I am doing the right thing before I proceed. I have gotten conflicting advice already from a couple people. some say get a speaker selector switch. someone else said I need an amplifier for the outside speakers. That seems to make sense to me although the selector switch may be a nice addition down the road if I want to control the kitchen separately.

Does anyone have any advice? If I do need some sort of amp what exactly do I need. I am a little lost here on all of this as this is uncharted territory for me.

Thanks Jeff for your answer. I should have also mentioned that I also disconnected the outdoor speakers and tried a set of speakers (indoor) that know work well. I did this just to see if the speakers were bad. It made no difference.

I also should have mentioned that when I was looking at the house prior to buying the homeowner said something about an amp for the outside. I just politely nodded as I really did not understand entirely what he was talking about. Being that the wiring is a long run to the outside maybe it is causing a drop in signal? Is that why he used an amp. It makes sense but like I said I am new to all of this stuff.

I just do not want to spend money on something if it is not going to cure my problem.

The receiver I have is an onkyo TNX709. I will try what you said about disconnecting the kitchen speakers. I also picked up a pair of Insignia NS-2111 Rock speakers to put by the pool last night. They were affordable and will blend in nicely with the landscaping I have. From what I read they are OK speakers for the price and it is just around the pool and outside. I have to admit this has been an education for me. Some of this stuff is really expensive. Best Buy had another pair of simulated Rock speakers that were $250 for each speaker.