I went through this many times...
Right now I'm using the iLoud Precision 5 set. These are not the cheap plastic speakers but are handmade in Italy. They use DSP to tune the drivers and response and have built in ARC which means you can hook up a reference mic (included) and then tune them to your room. They also have some EQ or response options.
Sonically they sound way bigger than you'd expect, flat down to about 40 Hz which is crazy for a compact 5" monitor. I replaced a pair of Yamaha HS8's which are twice the size because the iLouds were way clearer sounding but could hit the same low end notes. You can hear Michael Nielsen compare them to his ATC's in his video...no they aren't as good but they are like 10-20% of the price.
Prior to this I tried:
Yamaha HS8 - had a pair of these for a couple years because I wasn't happy with smaller monitors. They sound pretty decent and have low hiss which is an issue with cheaper monitors. Good build quality as well. But they were way too big for my desk and for my room; you really need these on stands with plenty of distance for the sound to develop.
Genelec 8020 - had these for a few years, I actually still have them and need to list them for sale lol. Genelecs are bullet proof, insane build quality, great product. I found them to sound small and boxy and considered adding a subwoofer but those are like $1000+ to get in the door. I think the 8330 would be the starting point where Genelecs make sense, as you can add the GLM kit and tune them.
Adam T5V - tried these for a couple weeks, they sound good but the hiss was driving me crazy so I returned them. They seem built a bit cheap too. I strongly considered the Adam A7V but checked them out in a store and they seemed to have the same hiss. I wasn't going to drop nearly $2k on noisy monitors.
Focal Alpha 50 Evo - also tried these for a couple weeks, they sound pretty big compared to the size, are well built, and don't have a loud hiss. I did find them just a bit scooped sounding though and ultimately I decided to return them to get the iLoud Precisions. I would recommend these though.
JBL 305/306 - pretty much the standard for cheap monitors nowadays. I had the 305's for a few years and they are pretty decent for the money, especially on sale or used. They do have a bit of hiss and aren't as good as some people hype them up to be. The 306's I also had for a while and they are are less bright and more punchy. Again good speakers for the money but not super flat.
When I was speaker shopping last year, I did check out a pair of Neumann KH120's, the older models. Be aware that the new versions have DSP and the old ones do not, so they may sound a bit different. The Neumann's to me sounded a bit bright and kind of distorted. They were used so there may have been an issue with them, but that's just what I heard. I also considered the KH80's but those felt like a sideways move from the Genelec 8020's.
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TL/DR - if you have a $1k budget right now, look for a deal on the iLoud Precision 5. Sweetwater has them for $450 each right now marked down from $900 each. That's a great deal. IMO they are the best speaker I've heard for under $2k/pair and getting them at half that price new is awesome.
Otherwise I'd check out the Focal Alpha 50 or 65 depending on your space. I think those are good, big sounding speakers. Probably not the flattest but cool regardless. Or PM me about the Genelec 8020's lol.