Vintage worth the time to explore?

Add a pair of subs. Makes all the difference in the world at all volume levels. 

...and you can play this, so's not to strain anything.... ;)

https://www.youtube.com/watch?v=cRIfsFefatg&list=RDMMbhQRS6iy23w&index=19

😏

If you get something from the 70's what might be helpful for you is most stuff had a "loudness" switch that will give you that warmth at low volumes. The marantz you mentioned probably has one.

Why not open back headphones like Grado's for when you want to play it loud? If you don't want to try that, And I also second:

1) Not buying anything older then 10 years. 

2) Looking for a system with a loudness button/control, or at the least tone controls.

the klipsch and elac speakers both sounded bright to my ears. mebbe if you got yourself an older yamaha amp with the variable loudness control? that would allow you to dial in a select amount of "warmth" without overdoing it. if you have money, to be on the safe side, you could get a pair of rega brio amps perhaps driven by a tube preamp, that would definitely warm up the sound. you don't want to even think about driving 2 pair with the brio. or you could try a brio or an old KLH receiver [warm sounding] with the elacs in front and a hafler circuit for the kg3 speakers on the rear [as they are mellower than the elacs, you don't want bright in the rears].