The GBE 600 is a GREAT sounding amp. Authority and punch way beyond its power rating. A classic amp, in my book...
Whoops...forgot to answer the OP question.
I deeply admire the old GenzBenz stuff, and have several units....
I've had a 3.0-10T for almost 10 years. Great practice or grab-and-go for small stuff. I'll never sell it. One of the very few pieces of gear I bought new, and it's been incredibly useful.
I keep a Contour 500-115 in an out of state location, where I jam and occasionally gig with friends. That combo is a gem, which can hold it's own in small to medium bars (outlaw country band with tasteful drummer) without FOH. The price I was able to purchase it for, as a blow-out after Fender pulled the plug on GB, was literally insane. Those Contour units could have RULED the giggable combo sector, but for Fender killing GB.
I have a Shuttle 9.2 saddled to the 12T.2 cabinet, and the second non-saddle cabinet to match. I don't often use the two speakers together, because if I'm in that zone then I usually grab an Audiokinesis cabinet, and likely another amp (thunderfunk or mesa D800+). But in situations where the 1-12 will suffice, it is an amazingly effective tool, and as a grab and go it is so incredibly convenient. I particularly like it when playing in multi-band or other dodgy situations, where theft of an untethered Class D amp would be all too easy. The Shuttle 6.2 is also a great amp, but the extra authority of the 9.2 is not subtle, so long as I am not stupid about the volume into one cabinet.
And while I use the Mesa 800+ amp, I've heard and played through Genzler stuff, and it also is superior!
Finally, I will confess to having a GBE 600 in the closet. I'm not likely to take it out so long as I have the Thunderfunk, but it was so darned inexpensive (used, of course), and sounds so darned good, and I really like to have some old lead sled in the house.
So Genz Benz is a defunct company that nevertheless keeps on giving - through the continuing value of the original products, and through the successor gear designed by Andy Field and Jeff Genzler, at Mesa and Genzler, respectively. And Field's continuing support of GB product is extraordinary. These gentlemen have a lot to be proud of!