I truly believe that the DNA .5 is overall the best sounding of the McCormack series (and yes, I have owned them all, in fact, a few more than once)The upgrade to Rev.A will remove the remaining tiny little bit of grain and allow for a touch deeper soundstage. One caveat, the revision does make changes for the better overall but it is not a leap into nirvana. I have known some who didn't like the revision when they got it back. Whether they gave it sufficient break-in I don't know. It does make a difference. Before, and I know, like me, you like McCormack, you might want to look at a few more amps before you spend the money.
To give you an example, I was using a pair of DNA .5 Deluxe amps to biamp my Vandersteen 3A Signatures. I was using an Audible Illusions preamp. I too, contemplated upgrading the 2 amps at a cost of about $2800 at the time. The amps themselves sold for $1495 each and had a current market value of about $700. I decided after reading Richard Hardesty's review of the Theta Dreadnaught to purchase one and give it a go. Man, what a move. I went with 4-200 watt modules for biamping. It was probably the best move I ever made. It enhances the basic McCormack sound to a genuine higher plateau. More transparency, bigger soundstage, pretty much, you name it. I then tried a borrowed revision A McCormack. I went to 2-ch on the Dreadnaught to make it fair. As much as I hate to say this, the comparison ended pretty quick. The bottom line for me was, the 4-ch Theta cost me $3900. A 2-ch at the time was $2700. These are with discounts through the "Sound Broker" brand new in the box. The Theta is a better sounding amp hands down!
The point is, I would look around a little before spending the bucks.
As for converting to a mono block, I would just go with the DNA 1. Even though I don't feel the DNA 1 sounds as good in direct comparison to the .5, you will negate some of the sound of the .5 doing this to where they both will sound similiar.
The new DNA's are excellent amps but I feel do not sound overall as good as the older amps. The new amps use a DC blocking cap in the input and you can hear it. They simplified the circuit somewhat.
Just my opinions for what there worth. I'm sure someone will come back with some other ideas.