My turn to echo JSHRED ...I have a Mesa Roadster and a Mesa Solo 50. In my opinion, the Mesa Dual Recs are some of the best amps you could get for the money. Don't feel silly for not knowing this stuff either. Playing 20 years doesn't mean you should automatically know this stuff. I don't profess to know everything. It's always going to be a work in progress for me. I don't see me at some point going: Ok I'm all set ...never have to buy another piece of gear, amp or guitar again. LOL
I was a Marshall guy for years, but I never had an actual Marshall "tube" amp. I had a MF350 that was loud as fck, but extremely difficult to get a good tone out of. The cleans were horrible, but honestly ...I don't think the cleans out of Mesas are all that great either. Maybe I just don't know how to EQ a good clean tone lol. So I ended up in a band with this guy who plays out of a Mesa Triple Rec. His guitar cut through the mix so much better than mine. I was going to get something like a Marshall JCM, but the day I went to plunk down, I did what you did and played on all different amps at GC. I played the Marshall, Blackstar, and then when I played through the Roadster I was like " aaaah this is the one." I then held off on buying that day. I went home and did some research online and youtube and stuff ...then went back and bought the Roadster. Then I wanted to get a 2X12 cab and ended up buying a used one off Craigslist, but the guy wouldn't sell me just the cab. He insisted on selling me the Solo 50 too. So I bought the rig planning on selling it, but after gigging with it a few times, I ended up keeping it. It's a badass little amp! So who knows how you'll end up finding the amp you want to settle on, ya know? But again ...like JSHRED said: just try as many as you can and don't let anyone pressure you in to buying something. Good luck and let us know what you settle on!