Upgrade path

If if you have the room: bigger Dunlavys,...or sub-woofers.

Keep in mind the value of your current Dunlavys.
Others might disagree with your power observations with Dunlavys, but you might(!) be on to something. I had a friend go from two 200 watt mono amps to four identical factory matched of the same amps, and the improvement was much greater than either of us expected with his SC IV's. I'm still not sure whether it was the extra power, the longer Class A bias, or some combination there in. 
The SC IVa' are capable of more of the things you are seeking than you might think. Unfortinately they don't show up on the used market too often. The SC V's show up more often and usually for less than $6k, so with the sale of your IV's you should be within budget. One caveat: a lot of V's and VI's were used in recording studios and might have seen a lot of (ab)use.

Not a fan of the Macs. Excellent build quality, plenty of parts, and service techs, but the sound to my ears is lifeless. And though with such copius power it might not matter too much, but sacrificing the otherwise advantages of frequency linearity of ss to accommodate auto-formers is non-sensical to me.