Hi I have a Vintage Marantz 1072 passed on from my dad... i think they are are from a similar period. Marantz all have that full warmish rich sound from that era I think... but what i found after doing some A/B testing with a new CDP was that the marantz was capping performance of both at a level... a pretty average level
I tested my technics SL PG590 (an inexpensive CDP) vs Audiolab 8000CD ( new £400 CDP which uses a decent DAC inside)
After A/B testing on this i could not make out which CD player was better.
I then switched the amp over to my crappy TEAC AG 790A which is an awful bassblowing lousy harsh sounding amp, and then i noticed with the A/B test with CDP's it was clear that the marantz was somewhat capping the performance of my audiolab to the same level as the technics...
The moral of this story... I'm not sure, as I havent tested it with your tube amp... but I believe classic marantz from the 70s/80s - unless the very expensive ones, look very pretty, but don't sound very articulate compared to todays standards. I found a manual somewhere of my 1072 on a PDF - it was like finding goldust I was so happy!!! 
But then I read the Specs and everything seem to make sense... i'm no expert but the figures of freq response and TDH etc did not match up close to budget amps you can find today for $150 like my TEAC. And then I was humbled...
My advice would be if you want to know whether your millet makes a difference take it down to a store and test it on other integrated amps that have pre-out... try not to try this on an expensive integrated amp,, maybe something that is at the same value as your marantz...
Edited by Brumagician99 - 1/7/11 at 10:21am