The thing to grasp with the LS3/5A is they are amongst very, very few mini-monitors that sound truly superb with a relatively small valve amp. There are many, many very good small speakers out there, but most of them force you to use solid state muscle amps, which for many of those drawn to LS3/5As is just a total deal-breaker. My 10-12 Watt Stereo 20 or TL12 Plus sound seriously good driving them, and they’d not stand a chance into many reactive ported 4 Ohm modern minis.
The opening post is seeking a small speaker for a Radford STA25, which is a far more powerful amp than my Leaks, but even so LS3/5As need to be on the list. I’d also look at whatever ProAc have as their current Response 1SC replacement (D2?) as they were always valve-friendly speakers, and I’m sure there are other options, but many modern small speakers really are non-starters that will suck all the life and magic out of a nice valve amp.