Mission to mix on an SSL level.

I have been trying to figure out exactly how SSL boards are able to get
a much cleaner mix. Is it all just the engineer? Is it just the equipment?
Well, I came to the conclusion that I has to be more than just the equipment
Because I have heard some pretty good home recording engineers who get
a better sound out of a $2000 studio vs. a $2 million dollar mega studio.
When I first began recording, I thought I had to purchase an SSL board, Neve Pre- amps
Nueman mics and so on. But I learned that with a pretty good pre-amp, Mic, Interface, plug-ins and a great computer one can achieve a pretty close sound.

Question: How do I determine if my room is the right size for a studio again? I forgot how you explained it.