As long as you know the room, and system as a whole, and can adjust accordingly, then you 'can' get equivalent results, BUT, that is a lot easier said than done.
Whole point of good reference monitors, in a well treated room, with what can be assumed to be normal hearing sensativity, is that you can trust your ears. If something sounds off, then you can hear it, adjust it, and know that those adjustments should translate well to other systems.
Thing is, most people don't really have great monitors, nor perfect placement, nor a treated room, and as a result, maybe your adjust the bass to where you think it sounds nice and full, yet not overpowering. Well, maybe your room and system as a whole results in not flat response, but a greatly hyped up low end....what happens then ? You hear your mix on another system and there is hardly any bass, or vice versa.
This is why its kind of silly seeing people drop $2k on a great monitors, but then go stick them in a corner, sitting on their desk, in an untreated room. You paid for the best monitors yet what your hearing is far, far less accurate than even something like a $150 M-Audio monitor in a treated room.
Diffusion panels are expensive though, bass traps are expensive too. Not realistic to expect many people to have a well treated room at home given the cost, and without proper measurement your still not sure what your getting.
What you can do though is at least follow some basic tips, such as don't put your speakers in the corner (see another thread) and don't put them right against the wall. Don't put them flat on your desk, get some isolation mats, they aren't pricey. Maybe put some drapes up over the windows (wife will be happy to do that I'm sure) etc.
Little things to at least avoid any huge pitfalls, and still keep a shared use room looking like a normal room and not a recording stuff (unless your spouse is fine with that route!)
Regardless of what you do, learn your system.
LIsten to some well known tracks, concentrate on the mix, then go listen to that same track on a home stereo, through your car stereo etc, other systems, what differences do you hear ? Does the stereo field sound wider with more depth ? Do you still hear the bass, can you hear the damper pedal on a piano recorded acoustically etc ??
I've had systems that I learned were a little harsh or "forward", so where if I dialed things back on the highs, when I listened elsewhere it was a little muted. I learned I needed things to sound a little harsh on my monitors because that would mean it sounds just "right" on other systems.
Its not rocket science, but its a difficult skill to master, with a fair bit of subjective taste, and the good sense to know when to ignore one's own taste and make something that will sound good to most listeners, if that is the end goal
