I'm considering adding height channels to my setup. I currently employ M60s for (L/R), VP150 (C), QS8s on stands (SR/SL) and a single EP500. What Axiom speakers would be ideal for height channels based on my current setup? I would not be mounting them on a wall. They would be placed as bookshelves on top of the two entertainment piers flanking my television - which would put their base at approximately 6 ft high and just slightly inside my L/R speakers.

I'm personally considering M2s but would like the input of others on how they would hold up as height channels in either Prologic IIz Height or Audyssey DSX height configurations.

Other questions...

Can they be placed on their sides as a horizontal speaker (similar to VP150) or would this affect their sound quality? I think, asthetically, it might look better layed on their sides versus standing vertically. Plus, I thought it might be easier to tilt them on their side to point directly at the listening position. And I thought I might be more concerned with vertical dispersion rather than horizontal dispersion (similar to center channels).

What are others opinions on Prologic IIz Height vs. Audyssey DSX Height?

Do you think it is worth adding height channels at all? I cannot add back surrounds (my seating is directly against the back wall). And I do not have room to add wide channels ala DSX Width. Do height channels add anything to the soundstage and surround effects?

Thanks!

Bryan