I'm reserving this thread for in depth review. I will add to it hopefully helping people who were looking for the same thing I was. Even though the ag500 has been discontinued.
Let me first day I have owned a DB750 and hate it, along with my orange 200d and tiny terror 500. Seems tubes just don't do it for me. I seem to like the GK sound.
So I purchased a AG500 today just to compare to my GK. set everything to noon and turned her on. Sounded great, very similar to my GK.
After a bit of A/Bing. I found the Gk hand a better low end (below A) for the style I was playing which was flea like heavy digging in. I found the aguilar to be quite boxy. After playing with the Eq I found rolling off the low Mids to about 10:30 (as seen in picture) made this amp sound near IDENTICAL to the GK.
So far this is my review I haven't done extensive styles of playing, but so far these amps sound nearly identical.