The X-series box speakers have two driver X-LS/X-SLS and three driver (MTM) X-CS/X-MTM versions.
The two driver version can be built into a ported stand mount cabinet, X-LS and a larger ported floor standing cabinet, X-SLS. The main difference is the larger floor standing cabinet has more bass extension (plays lower); X-LS - 55Hz, X-SLS - 45Hz
The three driver version can also be built into a smaller sealed stand mounted cabinet, X-CS and a larger ported floor standing cabinet, X-MTM. Again the main difference between these two versions is the larger floor stander plays lower; X-CS - 70Hz, X-MTM - 40Hz
The main difference between the two driver and three driver versions is the three driver versions have a fuller more balanced midrange. This does not mean the midrange is bloated, just more solid and better sounding.
My personal preference for a box speaker in the X-series is for the floor standing X-MTM version and for full range sound (20HZ-20kHz) with a sealed servo sub for the bottom octave.
A sealed servo sub can also pair with the less visually imposing stand mounted X-CS for a full range speaker. This would be my second choice for an X-Series box speaker setup.
However, my first choice by far in the X-Series is the X-Statik (-3 @ 48Hz) with a sealed servo sub for full range. These really don't need to be pulled that much further into the room than the X-MTMs. While the X-MTMs need to be at least 12" - 18" off the wall and the X-Statiks need to be at least 36" off the wall, the 12-18" for the MTMs is measured from the wall to the back of the speaker while the 36" for the X-Statiks is measured from the wall to the front of the speaker. Since the X-MTMs are 16-1/2" deep, this means the front of the X-Statiks are only 2-8" further into the room than the front of the X-MTMs. If midrange performance is your bag, the X-Statik is the way to go.
The NX-Studio Monitor has a different type of presentation. It has been described by many as one of the best stand mounted speaker you can get. It is sealed so would need a sealed servo sub for full range performance. It also has higher quality components in the crossover standard compared to the X-Series.
Here is what Danny says on his website about the comparison between X-LS and NX-Studio: "The Studio is technically the better speaker but the Encore sounds different so its a little complicated. We believe the Studio is a better bet for listeners that cant bring speakers deep into the room. Again, they are sealed so they wont dig quite as low as the Encores as well. Both measure extremely well but where the Studios shine is what they are able to offer with the GR Neo tweeter, which is open baffle. All cymbal hits and top end extension will sound precise and 3 dimensional. The Encores can offer close to the same performance upgraded but cant compete with the laser focus and precision the Studio brings to the table. Heck, get both. They are both awesome."
If you fully upgrade the crossovers in either the X-MTM or X-Statik it's going to come down to taste. I know you didn't ask about the X-Statik but you would be well served to give it due consideration. Hobbs has experience with both an upgraded X-Statik and NX-Studio. Maybe he will chime in with a detailed description of their performance. Not so much which he likes better but a description of what he hears the similarities and differences to be. Even better would be to take a trip to Danny's if possible.
