The G-Flex 2X12 is hands down an amazing cabinet. It is basically a larger ported Thiele, but it has smaller voice coils that tame the top end of the MK amps nicely. I also use an ealry 90's Boogie 1X12 Thiele with the EV-12L. It is a great cab, but it does not have the projection of the G-Flex. It's much more directional where the tone comes out in front of the cab. The G-Flex gives a wider spread and fills the room. With the Road King's, Rectifier, IIC+,III and IV I have found the G-Flex to suit my needs more than the other four 4X12's and the Thiele. My plans in the near future is to combine it with a Mesa 2X12 or straight 4X12 and see how they blend.
My main setup has been a stereo rig using the 92 Rectifier and the MK III or IIC+ out into two 4X12's. With the G-Flex and the Mesa 2X12 I am hoping to pair down the size and see if it gets me close to my original tone or better. My current speaker cabs are a Soldano 4X12 slant in snakeskin with V-30's and a Mesa slant 4X12 with V-30's as well. I get stereo separation with a super secret TC Electronic unit and the tone is massive. I do not use any effects, but I may add the Xotic BB for a little extra push. If the setup is noisy I will use a Boss NS-2 which is very transparent and I like how it lets the reverb tail off for a nice effect on the MK side if the setup.
Good Luck in your search for the tone.