Technically speaking, the LCD-3 has "proper" bass as Chris to eloquently stated. But if you're looking for a "naughty" bass, then I can see why you prefer the TH-900s. On all of the amps I heard both, technically, the LCD-3s have "better" bass in terms of control, naturalness and detail. But the TH-900s bring it for the "fun" factor (while still offer outstanding control and I can see why they're so enjoyed with electronic music (a genre I'm just starting into at the age of 41). But another factor is that there is too much bass as witnessed on the FR graphs on the TH-900s while the LCD-3s are linear down to 10Hz (and the 30 Hz square wave responses look "ideal" on the LCD-3s).
In terms of what I'm amping them with, please feel free to check out my sig. I'm pretty sure that the GS-X is up to par for either.