Where should the Tubes Go in a Vintage Preamp / Amp System

Switching from a Sansui G-8700DB receiver (which overall, I am very happy with) to a separates system... I am going with a Dynaco PAS-3 (tube) preamp which will feed a pair of McIntosh MC2100 (solid state) amplifiers, set up as monoblocks.

I have heard conflicting opinions, so I thought I would pose the question here:

If you are doing separates (preamp / amp) and you are looking to add tubes to the mix -

Which is better, a system where the tubes are in the preamp, or where the tubes are in the amp(s)..?

And by "better", I mean where will the tubes have the most effect in providing that 'tube' ambience of sound..?

I always thought the preamp would be the better choice out of the 2 (assuming you are not equipped to go tubes on both preamp and amplifier)...since the preamp receives the direct signals from each piece of equipment and is the place to potentially 'color' the signal before it moves on to the amplifier...

If you have an opposing view, please explain why a SS preamp with tube amp is a better opportunity to add a little 'tube sound' to your system.

Thanks!