want to hook up 2 spkrs for each left and right.

Um... Don't, but if you do, the safest way to run them would be in parallel. In series would drop the nominal impedance down to 4 ohms and I would imagine dips into the 2 ohm or less range which could harm your amp.

neither.

If you have a preamp out, take the signal from the preamp out to a second integrated amplifier and hook your Mythos speakers to that integrated. This way, there is no extra load on your initial amp, there will be no impedance issues at all, and BEST of all, you can control the volume of your second speakers relative to you main speakers which is ABSOLUTELY critical to the quality of the listening experience.

This is what I do exactly and the 4-speaker 2-channel set up is a monster improvement over the two speaker 2-channel set up --- but you need differential volume control to do it right... so you need a second integrated amp.

Wiring speakers in series is the safer way not parallel. If wired in series it would double the impedance.If wired parallel it would cut it in half.

Yogiboy is correct.If you run parallel you take the chance of damage to your amp if it can't handle that lower load.

This is for a larger presence for the theater. It will not be used for music. My other system is for music.

Yogiboy is correct.

It should be mentioned for the record, though, that series connection will not generally give good sonic results if the speakers are not identical or very similar models. The reason being that the frequency response of each speaker in a series configuration will be affected by the impedance vs. frequency characteristics of the other speaker.

Also, regardless of which connection arrangement is used, if the two speakers in each channel are at significantly different distances from the listening position, comb filtering effects will occur, which are likely to have adverse sonic effects. That may not be important for your HT purposes, though.

Regards,
-- Al

A P.S. to my previous post. A solid state amplifier will only be able to deliver half as much power into 16 ohms as into 8 ohms. So depending on the power rating of your amplifier, to avoid the possibility of clipping the amp when using a series connection you may need to be a bit more careful with how high you turn up the volume control, compared to a single speaker situation.

Regards,
-- Al

Both speakers are identical and mounted one above the other. I am using a Sherbourn Receiver.

If thats the case then run them in series and the volume will be the same on all. No worry about damage of amp. Just remember that the power will be less so try it and see if it is sufficient.