I have the Sunfire 300 x 2 and the current source output sound is very much like a Tube Amplifier. Everything that Bob Carver said about this output is smooth and buttery , base is not as tight as the Voltage source but not sloppy eather. Very sweet sounding.
So if your thinking about the Theater Grand I think you will love it.
The peak current on this puppy is 138 Amperes. I also have the Carver TFM-75 at 1000 watts 4 ohms & 750 watts 8 ohms and even though the Sunfire is 600 watts 4 ohms & 300 8 ohms, 400 watts less than the TFM-75 the Sunfire runs neck and neck with the other amp!
The TFM will clip before the Sunfire, and the Sunfire can be bridged for insane power " I don't think the Theater Grand can but not sure" Anyways the Sunfire is one Hell of an Amplifier and if your in the market for one the Theater Grand on the used market is about $ 800.00 give or take.
I never thought I would ever match the TFM-75 but the Sunfire with all those amperes has and sounds great at that.
Give one a listen you will love!