I'm going to go through my blurb which may repeat a bit from above.
The first thing you need to do is figure out what you really have and where everything is. That is, saying you have a blue wire is like saying you have a pink car... It just doesn't tell anyone anything beyond the color.
You will want to determine what wires you actually have. Speaker wire, CAT-5, control, etc.
Typically CAT-5 is in a blue-outer casing and consists of 4 pairs of solid wires. This makes a total of 8 wires, and they look like this:
http://www.skycoms.co.uk/images/cat5.jpg
Speaker wire has no typical color of the jacket, but usually contains 2 or 4 wires which will be red and black. If four wires, then typically red, black, white, and green.
http://www.homedepot.com/catalog/productImages/400/b5/b527b7ab-4847-499d-bb67-5539512e48b5_400.jpg
or
https://www.shopping-headquarters.com/shop/pc/catalog/ctg\43083.jpg
Control wire is rare and would typically appear as very skinny wires in a case similar to CAT-5, but not in twisted pairs the way CAT-5 is.
Now, once you have identified all the wires, you need to make a list of where everything is and what it is.
ie:
Dining Room: CAT-5 & Speaker wire to box near XXX
Kitchen: CAT-5 & Speaker wire to box near XXX
Typically, from a single central location there will be speaker wires run to a location near a light switch and then up to the ceiling. The easy part is finding out that there are speaker wires run to a box near a light switch. The hard part is then finding out where the actual speakers may need to be in the room.
This is where you will have to do some homework and some sleuthing to figure things out. Perhaps get a fox & hound kit (tracer/toner) to trace wires.
http://www.valley-ent.com/pics/cabletonera.jpg
The real goal is to find out the complete wiring layout of your home and what is actually available (completely) before setting an agenda and making plans for what you will do.
Once you know what is there, then you can start to think about what you would like to do. Be prepared to adjust your wants based upon your budget, and be prepared to adjust your budget based upon your needs.
That is, at a very basic level you can get a two zone receiver, setup the main zone as a 5.1 surround sound, and pick ONE extra room to run off the extra two channels of amplification in many receivers as zone 2.
ZONES: Zones are defined as separate areas of unique audio in your home.
If you have a Patio, Garage, and Dining room, and they are always playing the same thing, at the same time - then that is one zone.
If you have a Patio, Garage, and Dining room, and they don't have to play the same thing at the same time, then they are 3 separate zones.
It is also possible to use speaker selectors to have a single zone with many rooms, but turn those rooms on and off individually.
Likewise, it is possible to completely separate all the rooms in your home into individual zones and allow control of each room from within that room with the right equipment.
Typical low end/entry level:
Two zone surround receiver
Zone 1 = Home theater area - 7.1 or 5.1 audio
Zone 2 = Output from receiver to amplifier to speaker distribution to volume controls in each room (impedence matched) to speakers in the walls/ceilings of each room.
This can be done for the price of speakers ($50 to $500+) per pair, and volume controls (less than $100 each) and an entry level amplifier ($100-$200 or so) and the receiver ($300-$1,000), and the surround speakers ($300-$100,000+). At the lowest end, really about $120 per room for stereo, and cheap surround for $500 and $500 or so for the receiver and some extra cash for misc parts. Under $2K total.
At the top end is individual zones of audio with good speakers in each room. $200 per pair of speakers (at least) and a contrller/keypad in each room ($200ish) and separate amplification for each room (200 per room), and a controller with multi-zone capabilities ($1,500 or so). A 6 zone system with good surround and receiver will pretty easily cost $8,000 or more.
What's the point of the nicer system?
The biggest things are that it is typically REALLY easy to use the nicer systems and they are phenomenally reliable. My wife, in-laws, and kids have no issue listening to music throughout my home.
The downside is price. It can also be something of a process to upgrade parts and pieces.
There are hybrid systems you can put together which have multiple zones, and multiple capabilities. Somewhere between the cheap and the really nice. But, it really is more about what you want and what you can afford instead of what the limits of the technology are. You should have lots of options available to you.
I wnated to add that speaker brands don't matter. Really, don't care what speakers you have. Good speakers costing $1,000 typically sound better than $50 speakers, of course, but they almost always hook up and are connected the exact same way. So, if you want speakers in your laundry room or bathroom where sound echos and never sounds great, you can go with far less expensive speakers compared to other rooms which may benefit more when you spend more. Don't focus on the brands, and be aware that there are often FAR cheaper alternatives out there, especially online, which may make you really happy for the money spent.
Check
www.partsexpress.com and
www.monoprice.com for some concepts of pricing and parts.