So many comments made, but I figure I might as well chip in since I'm using the same "cheap" monitors as you. I pretty much just use the presets, but I believe (and someone can correct me if I'm wrong) that the presets are basically Fractal's opinion on the "typical" sound or use of amp/channel x/y/z. So imagine someone set the amp down in front of you with the treble down, bass up and mid scooped. You play through it and don't care for it. What you'd do is reach over and alter the treble/bass/mid. This is the same thing, it's just a different way of doing it and there are more options.
If I could afford more expensive monitors, I'd try it. I'll have to try headphones and see if I hear things differently.
What I've done is just do some tweaking to get more of what I like. People have said you have to sort of deep dive into the settings, but really, you can access the tone controls and the IRs really quickly and easily and those two tweaks will make some significant alterations in the sound.
I believe that pickups can make a big difference as well. One amp sounds great with my strat. Clean and crisp. But if I plug in a guitar with a humbucker, then it pushes the amp that little bit to throw it into a bit of distortion. I believe that some amps change their color when you alter the volume with the volume knob on the guitar. For some reason it seems a tad brighter with full volume and a tad muddier with lower volume (on the AC30 top boost at least). Could be just me though. Either way, use your ears, play around with stuff. If you think about it, I don't believe you'd not mess with any knobs or dials on a physical amp that you have, so just think of the axe the same way. Tweak away and see what strikes your fancy.