Danny,
Both my wife and I really like the (as yet unpainted) LGK 1.0 speakers in our bedroom system. In fact, I like them so much that I've begun wondering about what else is out there in the single driver world. I'd be very interested if you had something else like a 5", 6", or larger(?) driver. Alternatively, if there is no such speaker offered by GR Research, would you be willing to make any recommendations?

Michael
There are some disadvantages by letting the driver diaphragm size increase. The off axis especially falls off really fast. Stored energy is also a problem as moving mass goes up.
If you really want to take things up a notch then just limit how low the LGK has to play and let something else handle low frequency duty.
I had a pair of the LGK's on stands about a foot out in front of a pair of Serenity Acoustics Super-7's. I played the four 12" open baffle woofers of the Super-7's from about 90Hz and down with the little LGK's while filtering off the lower end with some inline filters. I know, that's crazy huh, but the results were stunning.