Zu Audio Omen MKII

II's are always better than I's. Or at least they should be. I know that my Druid Vs sound significantly better than the IVs. 
Just call Zu. You will get honest info. One of the many things that I like about Zu gear is that it is constantly evolving. When they make improvements to their products, they pass it on to the consumer in a fair manner.
Zu has paired their speakers with Peachtree amps at audio shows if my memory serves me.
Enjoy!

early,

I would like to know in which aspects the Druid Vs sound "significantly" better the IVs.

Hi jesusaO,
You should check out 213Cobra's post entitled Zu Druid & Definition Roundup.
He addresses the differences between Druids at the beginning of what is a very long post. 
It's very good.
early

Hi brimel,
I don't own Omens but I own 2 other pair of Zu speakers (Superfly and DefHead).  I can't answer your question directly, but I have upgraded the drivers on my Superflys, so I can offer some perspective.  The new drivers on Omen mkII should sound subtly but noticeably better.  In my own experience, the new drivers were just a touch more effortless, a bit more oomph (or "shove" as Zu likes to say), just a bit more "there".  Again, subtle but noticeable.  

The key word is "subtle", meaning if your budget only allows for a used pair of mkI, don't feel like you are missing out on a world of sound.  Your best bet might be to wait until Zu offers their $999 Dirty Weekend II sale again, those now use the new drivers but without the upgraded capacitors and level of fit/finish in mkII, which you can see in the chart here:

http://www.zuaudio.com/loudspeakers/omen-dirty-weekend-2

My personal take is that you get what you pay for with the mkII upgrade but used mk1 is still a nice entry point.  It's up to you to decide on the tradeoffs.

Zu does shows with Peachtree all the time so your amp should be fine.