Is Pre-Amp needed

The ARC preamp provides more of everything, especially the layering of instruments.

It can’t make something from nothing, all it can do is to add colouration/distortion euphonics if you wish to call it that. If it’s not on the recording a preamp cannot make it. There is no voodoo in hifi!

I was pretty happy with the TVC for years. But when I replaced this TVC with an active preamp, the system gained musicality and life.

TVC's are a "transformer based volume control" your lucky that's all you disliked about them.

Cheers George

 THEIR source’s preamp

???  Sorry there's no such thing!
The output buffer in the source is the same if it has a digital domain volume control or not. And only if that volume control goes below 75% of full does it start to "bit strip". 
Many hiend source counter this by have a gain setting for the buffer stage, so then the digital volume control can be used at or above 75%. And if you have one that doesn't have the buffer gain setting or digital volume control the the answer is to leave it at full up and use an external passive volume control.

I have a $11k retail DAC which has a very nice analog output stage and volume control. It sounds really nice amp direct. It sounds even better through an Audio Research Reference preamp. YMMV.

If that's the case then you don't like the sound of your source direct, and need to colour it with the AR preamp's colorations and distortions. 

Cheers George  

mrdecibel
I will never use a preamp again.

kalali
Never ever say never. It may be that you’ve not yet heard the right preamp for your system.

Maybe he’s like me and has a source he loves the sound of, and doesn’t need to colour it in any way by adding a preamp? Unless he could get one of those fabled preamps that have no sound and sounds just like a piece of wire, wait a second!! then that would be??? yes!!! like going direct!!!!

bdp24
What are the requirements for a source component to be up to the task of driving a given power amp?

Enough output from the source to get it loud enough for you (which most are).
And a min of 1:10 impedance ratio, for output impedance of the source to the input impedance of the poweramp (which most are).
And if you don't like it, you don't like the sound of your source.

Cheers George

A preamp can never make the sound more accurate, it can only degrade

This statement is 100% correct. Going direct, has less distortion and colouration, is more transparent and dynamic.
An added preamp preamp, if prefered can only add colourations/distortions as a "band aid fix" for a "source sound" they don’t like.
Get a better source, instead of putting a very expensive bandaid on it. "The best preamp is no preamp."

Cheers George