Jay,
Without offending, I doubt Fitz is doing this mod. He talks like its the greatest thing ever, but if I rember correctly, he is just reducing the hum? Two damn resistors on the AC heaters to ground will take care of that.
And the Extreme is a bit different than the DV. As I mentioned the Extreme has parallel output tubes, and better quality parts. Now its up to you to decide if all that makes up for the price difference. Depending on the power supply (specifically the current capability of the heater transformer) in the DV, it would be about a $15 job to modify it to parallel the output tubes.