You would have to make sure that any speakers you might get never go below 4 ohms throughout their entire frequncy range. The higher the speaker impedance throughout its range, the better. This is why I often recommend going with the following speakers that meet this criteria and are also excellent sounding:
Coincident Technology Triumph Extreme's and using the Coincident passive sub-woofers as their speaker stands. This makes a great full-range monitor speaker.
Coincident also makes tower speakers that are similarly very easy to drive and are outstanding performers.
Mr. Israel Blume, the designer and owner of Coincident Technologies could make some excellent recommendations and is great to talk to.
With Vaughn speakers one buys direct, giving you very good bang for the buck. The top of the line Cabernet's are excellent speakers and very easy to drive.
Devore also makes very good easy to drive speakers.
Fritz speakers makes some excellent transducers, is easy to talk to, and since he sells direct you get some hellaciously good deals. Again, he could be very useful in guiding you through this path.
Of course, there are many others, but the above make a very compelling starting part--if not a great end point.
Greg