Let's be clear: there is no one single factor in your audiophile system that affects your sound more than your room's acoustics. Walls, furniture, carpets, art on the wall, and all sorts of other considerations make your room uniquely yours.
But how many of us get to design our room to be acoustically excellent before we start moving in our audio gear? Not many. If we did, we would have installed double studio doors that locked out external sound. We would have redone our drywall with "quiet rock," which makes a room almost sound proof.
And for this can be done for a few thousand dollars.
We would have put a hush-kit on our HVAC system to keep that noisy AC fan from making too much background noise. We would have installed the quietest of lighting control systems with zero hum in ways that wouldn't offend even Ned Flanders. We'd also have more than one dedicated, deeply grounded, AC power circuits
For optimum isolation, integration, and aesthetics our gear would be located in an equipment room; much like Bel Air Circuit home theaters have projection rooms where the $100,000 Christie Digital projectors are isolated from the viewing space. Windows would hush upwards of 30 dB of outside noise even from the loudest streets in Manhattan or Tokyo for an optimum the listening experience.
We all know, regardless of our subjective/objective slants that the quieter the room, the better your equipment is going to sound. Unless your room just happens to be an anechoic chamber...
RPG's Modex plates eat bass waves and can be screwed into the corners of an audiophile's room into the stud-bays by a hobbyist with stunning results. Whisper Walls make for a somewhat affordable modular system that creates a somewhat absorptive fabric wall surface throughout your listening room that isn't terribly expensive. Pleasing to the eye, Guilford fabric is tightly stretched over rectangular frames and looks gorgeous. You can even install blue-jean-like absorption or more diffusive surfaces behind the walls that nobody can see which can reduce nasty audio maladies nicely.
On the ceiling, you can install the most expensive (think: $125 per can) lighting elements that are virtually hum-free. Add an affordable Lutron and you'll be able to dial the lighting in to exactly the right level for your listening pleasure.
And yes, audiophiles, it's time for us all to dive into the exciting world of room correction. Companies like Trinnov, Dirac, Anthem, and others are offering digital filters that make today's $1,300 AV receiver a more powerful audiophile preamp than many of last year's $10,000 non-room-correction models. There, I said it.
Understand me clearly. It is far better to address acoustical maladies in the physical domain first and use FIR and IIR filters later as scalpels rather than sledgehammers. Well-done room correction can take you from "almost there" to "all the way there" in less than an hour, and without much added expense.
But to get to the best your music can sound, you need to get your room right. Affordable upgrades to your listening room are the least expensive and fastest way to get the biggest upgrade your money can buy. Embrace it. please...