Low priced giant killers

Platinum Audio Solo's are quite fine, and you really get to enjoy the bass foundation in all your recordings. Because the company is gone, the used price is in the $600 range. Your 90 watt tube amps are going to be able to power these in their sleep, as I used 35 watts per channel in a twelve by fifteen foot room, and never felt restricted dynamics or extension, despite some Audiogon warnings that only mega-amps need apply.
There was something very special about the overall presentation that really could fool listeners into guessing their used price must be much higher.

Used, obviously, Magnepan IIIa's. Nothing else mentioned is in the same league. Read old reviews of these. We just helped a buddy put in a budget home theater and found some of these. Just a tremendous speaker.

I agree with Albert on the Kirksaeter Silverline 60's. Also, the Totem Tabu used is just above that range. A very capable monitor.

If it must be small, Spendor s3/5 are a really good HONEST speaker under $1k new, around $600 used. If you can go with a modest bookshelf your options open up considerably.

I just picked up a set of Audio Physic Sparks (original model), beacause I was looking for the same thing, basically. These babies simply jump into the room with a huge, spacious soundstage and a ton of detail. I can't imagine getting more speaker for less money, EVER!