Need advice on speakers and AV receiver with independent zone 2 function - please???

We are NOT audio tech savy people but we are trying to purchase our first ever AV receiver and rapidly getting very confused! We have already purchased and installed two Klipsch R-1800 C in-ceiling speakers plus two Klipsch AW-400 outdoor speakers for our deck but now need to purchase whatever else is needed to complete the system - AV receiver, floor speakers, bookshelf speaker, subwoofer?? We would probably like to remain with the Klipsch brand for speakers but have no idea which receiver we should purchase. We already own iphones, ipads and a mac book pro so being Apple-friendly is important. The system does not need to be "fancy" but ideally we would like to be able to have the tv running inside while playing music (does not need to be HD) playing outside - is that what is called independent zone 2?? Any advice would be greatly appreciated! Thank you.

Thanks for your welcome! I've already learned a lot from reading some of the information on here! The current in-ceiling speakers are behind the couch. We only need a simple set up so five speakers is fine. Our budget for the AV receiver is around $500?

All very helpful information - thank you!! However, I am not sure if I have made myself entirely clear. From what I can gather, we don't need to have HDMI capability on the extra channel as it will only ever be used to play music outside through the two outdoor speakers. The only scenario when we would have the two outside deck speakers operating at the same time as the inside speakers would be when we may want to have a football game on the tv inside going at the same time we are playing music outside through the two deck speakers.
I think I remember being told at some stage we would need to get the additional speakers (sub woofer plus floor/bookshelf pair) to get a "complete sound" when we are watching tv etc. Won't there be some kind of delay between the in-ceiling speakers and that which is played through the tv if we don't?
From what I can gather, ideally we need to purchase the extra sub woofer and floor/bookshelf speaker pair plus a 5.1 receiver with an independent extra analog channel (ie a Zone 2 with a minimum of two outputs?) but I don't think this configuration exists?
NB We will be running our cable tv, DVD player and Apple tv through this set up also - all music will come via itunes on our ipad, Mac book or iphone through airplay or the apple tv (I guess?!).
Any further advice?
A Yamaha rep suggested I look at the RX-V773WA as "it can do 5.1 and 2 speakers in the main zone. It also has analog outputs. It has party mode so you can send out all signals to all speakers at one time." But I'm not sure if this is a little over the top?
We don't want to have to buy extra amps to power the two outside speakers if we don't have to?