I leave mine on at all times as well and have a sub for each system I use. The KRK 10 is awesome....I have one of those as well. The key is to not use too much. You want to hear a little low end but you don't want to FEEL much of it.
Put on a CD that you know really well and just turn up the sub until it sounds good to you. If you can feel it, you're using too much. From there try a few mixes and see how you fair. If you are bass light when you listen back on other systems, lower your sub and try again.
If you are bass heavy on other systems, turn up your sub and mix again. The hardest thing about the sub is deciding what frequencies you want need to accentuate. At my home studio, I'm pushing 85 Hz as that's what my room needed. At my real studio, 70 Hz is what we needed. You'll need to experiment a bit...but once you dial it in, you will never have to learn anything again.
Speaking of that, I've seen "learn your room" or "learn your monitors" posted a few times on these forums. For what it's worth, I have to sorta disagree with that. If you can tune your room and your monitors, there should be no need or reason to learn them really. If you can't, then yeah, I can see that. But keep this in mind...
When you have to learn something...a room or a set of monitors, you are forcing yourself to compensate in a sense. That's not how this field is supposed to work. When you tune your room and eq your monitors for flat, the only "learning" you *MAY* need to get used to, is what a flat and uncolored experience is supposed to sound like. If you've spent your life with bass boosters, excessive EQ and 3D enhancement or wideners in your media players or stereo systems, you're in for a rude awakening.
That said, when you are in the right room, what you hear should be what you hear. When I was learning to do this stuff, I'd go to a killer studio to listen to the mix I did in my home studio only to hear all the mistakes I made. The reason being? The pricey studio had a tuned room with monitors corrected for flat. When I listened to something I did, any mistakes were blatantly obvious. I wasn't familiar with that room or those monitors. They just sounded great and everything I listened to on them commercially sounded great too. My stuff was a notch above suck to be honest.
As soon as I did that tuning and correction to my studio, I was instantly able to hear the right stuff and make the right calls. There was no learning the room for me, honest. I listened, I heard, I made corrections. Those corrections stuck and sounded like the mix I did in my studio everywhere I listened. That's how it should be. This field should never be about learning to where it actually means compensating unless you absolutely have no other choice. My man cave is a 12x12 room. It's nothing to brag about. It sounds as good here and is as consistent as my big studio down the shore that has bass traps and Auralex all over. When I listen to something I did at my house at the real studio, it sounds as it should and vice versa.
If you have to compensate, it's probably time to fix your room and your monitors. If you can't....it's like bringing your CD out to your car and taking notes and then bringing the notes back into your studio while trying to make changes you can't even really hear in your studio. We've all been there. You are then forcing yourself to "learn" your room/monitors...which if you think about it, is silly. How can you try to fix something you can't really hear? Ludicrous, don't ya think? That's what "learning your room/monitors" means to me.
I'm sure there may be several that disagree with me, so I'll say this. If you are struggling with your mixes, call a studio you trust that has good gear with a tuned room and corrected monitors and ask them to book you a listening session. They'll either charge you nothing if you go on their down time, or a VERY small fee. You'll only need 20 minutes tops. (Heck, come to NJ and hang with me for the price of your gas and travels.) Tell them you just want to listen to the stuff you have recorded and mixed on your system, on their system. Take notes of what you feel you did wrong, and then ask them for their take. If you go in the right room, there is nothing to learn! You just "hear it" and know what is wrong.
I don't have any awards other than writing the longest posts on the Sonar forums, but everything I mix and master sounds the same everywhere (good or bad, I'm VERY consistent! LOL) I play it other than on laptops. I've never heard commercial recordings sound good on them either...so I don't feel so bad for striking out there. :)
-Danny