I have a McIntosh preamp with defeatable tone controls. I think of them like air bags in a car that only deploy when needed. In audio, that means when the source material is poorly recorded or in poor condition, but you want to listen to the music anyway. About 95% of the time, I use the tone bypass feature, but it is nice to know they are there if needed.
I love the Mac sound. I also bought mine used. The beauty of buying used is that if you aren't happy, you can usually resell the item for most, if not all, of what you paid for it.
I say, go for it. I like tubes, but the least expensive Macs are the solid state units that came out in the late '60s through the '80s. They are well built, but some parts do age, which can affect, or destroy, the unit's performance. I got mine from AudioClassics.com. They specialize in used Mac gear, and service what they sell. Give Ryan Kilpatrick a call. He's a terrific guy and knows his stuff.