Many of the other guys here will probably be able to better help you if you are looking to select a particular brand of speaker, but maybe I can help you with your connection question in series vs. parallel.
For a typical receiver, hooking speakers up in parallel is generally not a good idea. What this does is effectively drops the impedance of the overall load as follows:
Where Z = Impedance
Where Ztotal = total impedance
Where Z1 = Speaker 1, Z2 = Speaker 2 and so on...
When you place any load, whether resistive or inductive (as in speakers) in parallel, you are effectively reducing the load (impedance) by half of the rated impedance load of one speaker (if wiring two in parallel, with the same rated impedance), or by the equation below, if using more:
Ztotal =
_____________1__________
1/Z1 + 1/Z2 + 1/Z3 + etc...
In Series Ztotal is simply Z1+Z2+Z3+....
So for the above, if you are wiring 3 speakers in parallel (each rated for 8 ohms), the end total impedance the receiver would see is around 2.6 ohms.
It series, for 3 8 ohm speakers, the total load would be 24 ohms.
Why is lower impedance bad?
This is where Ohm's Law comes in. Ohms law states that there is a linear relationship between a circuits source voltage, current and resistance (impedance).
This relationship is described as E = IR (or Z for impedance)
Where E = Voltage
Where I = Current
Where R(Z) = aforementioned resistance or impedance
Therefore with a lower load such as 2.6 ohms, for a rated voltage, this means that the current in this circuit would have to increase.
I'm not sure of the voltage in a given speaker circuit so I'll assume 15 volts.
Therefore to solve for the current: I = 15/2.6 ohms which is 5.76A current
(This is the parallel scenario)
In perspective - a single 8 ohm connection would yield I = 15/8 ohms = 1.88A current.
This means more current is being supplied by your amplifier, which could lead to some very undesirable outcomes (in the way of burning something up).
As I understand it, many modern receivers have built-in protection circuits that will cut off this scenario before damage occurs, but it's still not something you would want to do.
Also, keep in mind that a speakers impedance will vary over frequency - so the above numbers are based off of nominal rated impedance specs.
For ambient music; not sure if this is ideal for you; it would be better to put together a 70 Volt distributed sound system, then you can wire several speakers together off the same home-run, and achieve background mono characteristics. This gets into the rated power of an amplifier that can provide this sort of output - the combined power of the speakers should not be less than the amplifer can produce. Many in-ceiling speakesr (contractor series) I have worked with in the past have wattage taps built in to satisfy a wide variety of circumstances and scenarios.
I hope this helps clear up some of the confusion about the electrical side of things.
There are a lot of extremely knowledgeable people that use this site. You will get your questions answered by some of the best.
