I'm not sure I quite understand what you are describing - it seems backward to me. The set up I am used to seeing, across various sound systems is:
1. Musicians connect to a stage box (via DI box for instruments).
2. All those signals are sent down the "snake" (just a convenient way of keeping lots of individually shielded wires neatly together) to the mixer, which is towards the back of the church (so the engineer can hear what things sound like across the congregation).
3. Signals are mixed and sent to various outputs.
4. Monitors typically run off an auxillary send (and you can set up a mix independent of the main signal). That output is sent to an amplifier and thence to the monitor speaker(s). At my present church we have a couple of powered monitors (so the amp is inside the monitor) but at my previous place some of the monitors ran through a separate power amp - as long as the signal is amplified somewhere, everything is fine.
For any given signal, you should be able to trace it from the point of origin (instrument or mic), through different stages where it is amplified and possibly split into multiple parts (that is what each aux channel lets you do). If you can track the path of each signal, you should be able to figure out what plugs in where.
What I'm saying is that I think you are using "from" and "to" the wrong way round. Your Aux 1 send should be running from that socket TO the amp; otherwise you are using it as an auxillary input instead of output.
ps. Cord (or cable or wire or lead), not chord - the latter is what the musicians have to worry about and one of the things the sound engineer can leave entirely up them!
The chord goes from the snake (multicore) to the monitor because your multicore has both send and return channels, and is designed to carry signal back to the monitors as well as FoH power amp.
Can you clarify please - are the monitors self-powered or do you really have the power amp for them near the desk? That would be unusual. Normally the signal is sent at line level to the monitors from the desk (you can usually chose pre or post fade) and is amplified locally by the monitors themselves. You physically pre-set each monitor volume *to a suitable level* on the monitor itself, then adjust up and down as required at the desk, using each channel's monitor level control + the monitor channels master level controls.
Translating this discussion into "monitor is the LAST thing in the signal path" - ese...
He mentioned that the signal path from the power amps to the monitor speaker is running on channel #C on the snake, I think that means he's okay - some snakes DO have four 1/4" lines that can handle speaker level signals.
Sherron: if the "C" connector on your snake is a 1/4" plug (looks like a guitar cable), then you should be okay running a powered monitor signal through it. If it uses XLR connectors (three pins within a circular shield - then you should not run a speaker signal through that. Actually, if you HAVE been running a speaker signal through XLR connectors, umm, this discussion should explain why those channels on your snake aren't working any more :-)
As everybody else has pointed out, signal flow starts at the microphones, goes through the snake TO the mixer, and comes back to the stage through the mixer, with the speakers as the LAST thing in the signal flow. The cable between the power amp and the aux sends on the mixer is best described as running FROM the mixer TO the amps, and then, in your case, the output of the amps runs TO the speakers via the snake.
But, umm, quick answer, if you're hooking it up this way already and it's still working, then it's okay :-)
Unfortunately, the kind of connector on a snake send does not tell you if the snake is designed for powered signals or not. 1/4" connectors used to be the standard on consumer-level snakes/equipment, so there are plenty of snakes with 1/4" returns that are not designed to handle the signal from an amplifier. You have to search and search to find snakes that are designed for such a use (I think in over 10 years of working in audio, I've only encountered two - one was bought specifically because it could handle speaker signals for use by a local theatre company and the other was in a pile of broken cables that someone had asked me to repair for them.... )
Really the best way to check if it is OK is to look at the connections in the 1/4" (Male) plug. If the wires are small and one of them is wrapped around the inner cable, then it is a TS (unbalanced) line-level connector. If the two wires inside are both in their own rubber tubes and appear to be the same gage, then it may be a speaker connector.
Speaker cable will look similar to this: http://www.fullcompass.com/product/324386.html
Instrument cable will look similar to this: http://www.fullcompass.com/product/265070.html
I hope this helps.
It would be nice to get a clear signal path for what you are running now, so all of those who are confused about the 'To' and 'From' could have that clear answer to better assist you.