How do I get the "most" out of a speakers that are rated for 12 ohms?

Your amp is probably putting out about 100 watts into the Omens, which is plenty.

I am not surprised you did not hear a difference with the snubbers installed.  Omens are not that picky about amps.  The purpose of the snubbers are to flatten the impedance curve of the speakers and reduce the impedance the amp sees.

A couple scenarios where the snubbers are useful: 
1. Speakers are heavily damped and the amp has a high damping factor and bass response and impact is suffering.  Typically you might see this with the 16 ohm Zu models.
2. You're using a low powered amp that likes a flatter impedance load.

As far as getting the most out of them, if you enjoy the combo of your amp and the Omens, I'd play around more with toe-in, floor gap height, etc.

To be honest, I doubt you are delivering any more than one or two watts of power to those speakers-if you are listening at 'normal' levels.
Any excess power is/should be available to handle transient power demands.
Snubbers- I think you are referring to the resistors Zu offers for some of its' speakers are more for amps that perform better with a higher resistance, like tube amps.
Bob

My amplifier is rated at 125 wpc @ 8 ohms, 200 watt's @ 4 ohms.

I would infer from this that the amp is solid state. Consequently, depending on its design its maximum power capability into 12 ohms could very well be not much more than 2/3 of what it is into 8 ohms. But as Bob noted above that is almost certainly not an issue given the efficiency of these speakers.

Also, while the resistors will increase the amount of power that is put out by the amp they will not increase the amount of power that is delivered to the speakers. The additional power will simply be consumed by the resistors themselves.

Also as Bob alluded to, I would expect the resistors to be useful mainly in the case of some tube amps. In those cases providing the amp with an 8 ohm load might provide sonic benefits by optimizing the loading of the output tubes and output transformer. Also, the resultant flattening of the impedance curve whoopycat referred to is most likely to be beneficial when the output impedance of the amp is a significant fraction of the impedance of the speaker. Which is almost certainly not the case when a nominally 12 ohm load is presented to a solid state amp, and is most likely to make a difference with **some** tube amps having particularly low damping factors and correspondingly high output impedances.

Regards,
-- Al
 

Your speakers are designed to be used with low power amps.  You should talk to Ralph (atmasphere) for suggestions.  Ralph will say that your speakers are medium easy to drive (high impedance) and efficient (sensitivity), though.  Ralph says that as you increase the power of an amp you increase distortion, I think, I can't really speak for Ralph.  He builds amps and really knows his stuff.

Do a member search and ask him for his advice.  He is quite free with it here.