My thought is that one is better off exploring the used market for gear less than 10 years old. Most bang for the buck.
There are amps at the same price point as the Marantz that can bring greater dynamics to the sound. Loss of warmth and color? Maybe your speakers are the problem.
The only vintage gear I would consider is point to point wired tube amplification from the 60s, such as the Dynaco ST70.