Marshall Silver Jubilee 2555x Reissue is a tremendous value. It doesn't even cost as much as a JCM 800, but has a LOT more versatility. Reeves amps has very affordable Hiwatt style amps which sound absolutely incredible, so if you're in the market for one of the best boutique amp values, Reeves is in the top 5. Bogner makes the Shiva, Shiva 20th, Uberschall, and Goldfinger 90 which are all in your price range. There's no argument that Bogner is one of the all-time absolute best. Friedman doesn't really have a great value amp per se which is unfortunate, but the used market is where it's at if you want one of those.
Badcat amps don't get talked about much around here, but they are a staple in the amp world. My God man, the Hot Cat 30 is absolutely incredible, pure Class A bliss. It's versatile, delivers the goods at any volume, and you can rock the hell out of any song with it. They're only around $2200-2400 depending on if you want reverb.
Divided by 13 amps are super great sounding, superior construction, and really aren't too bad price wise. Many of their amps use smaller tube types like 6V6 and EL84s, but they also have several models which use big bottle tubes. They may be relatively simple amps by today's channel-switching standards, but man do they sound good.
The Engl Artist is a HUGE value. Such impressive tone and pretty damned versatile. They offer plenty of value, but if you can get your hands on an Invader II, snag it! Blackstar Series 1 is another incredible value. Though Blackstar prices have inflated too much for Chinese made amps, they somehow still maintain great reliability. The Series 1 100 is a classic by now in it's own right.
I have to give Soldano a mention because the Hod Rod 25, Hot Rod 50 & 100, Lucky 13... are all great values. We're talking legendary tone, and by todays pretentious boutique standards, they aren't that ridiculously priced anymore.
Two-Rock makes several REALLY great amps, including the Sensor which is a closet high-gain monster. It's such a versatile and amazing amp, and you can get incredible deals on them. The Studio Pro is amazing, and with a few pedals, you can do so much with that amp.
Lastly, I'll include a couple of honorable mentions. EVH amps are an amazing value. The 5153 and Stealth won't get you shunned by the gear snobs because you kind of HAVE to respect them. Lastly, the Vox Night Train 50 is an absolutely incredible value. Man it sounds so damned good and you can get one for such a great , great price. It's amazing that they haven't been discussed on this forum because you just can't discuss the best amp values without mentioning the Nigh Train 50.