This question has been in the back of my mind for a long time. I've only ever used a single sub setup so I wouldn't know.

When an amp is powering 2 or more subs does the amp's power get divided by the number of subs it's powering? For example, would a 200 watt mono amp give 4 subs 50 watts each? Or does each sub get 200 watts?

I really don't know the answer to this question so if someone could enlighten me that would be great.

thats right, the amps power would get divided just how you used it in your example

yah man it goes like that

No. Not at all actually.

Lets say you have one 4ohm sub hooked up to your 200watt mono amplifier
If you add another 4ohm sub (wired in parrallel) this now presents a 2ohm load on the amp.
If the amp is stable to two ohms then it is possible that the amp will now put out 200watts to both subs. (but more likely 150watts per sub)
If you hooked up the subs in series, you present the amp with a 8ohm load, in this case the amp may put out 100watts to each sub.

Confused yet?

It also has to do with the amps ability to double the power with less resistance.

IE: A US Amps 100HC is 1 ohm mono stable. It's ratings go:
200 x 1 at 4 ohm
400 x 1 at 2 ohm
800 x 1 at 1 ohm

This amp has no problem doubling power output to the sub because the way its built (power supply size and quality, output transistor quality/type, etc).

On the other hand, take a different amp from the pile, like a Sony XM-2100G:
100 x 2 at 4 ohm
180 x 2 at 2 ohm
240 x 2 at 1 ohm

See how the ratings don't double in this case? It has to do with how the amp handles the load as well as simply adding more drivers. Likely, manufacturers step down the power output by current limiters and circuitry to allow the amp to be more stable at lower impedance.

Yes well i figured he knew that the amps power at the given ohm that the subs load would be, would be divided. confused?

Basically, whatever the output is of the amp at the given load (of the subs) will be divided by the number of subs.