I've used the same Polk Audio RTA-12Bs and Hafler DH-200 for the last 27 years. You can buy an old DH-200 on eBay any day for a little over $100. Nowadays I use ASC Studio Traps in an Attack Wall configuration to control early reflections with the monitoring triangle at about 1.5 meters and even though they are "floor standing", I have the RTA-12Bs on 16" tall stands so that they are at the correct height for monitoring.
I really have no use in the monitoring room for small "studio monitors" with no bottom octave. I'm OK with systems like the Blue Sky where they engineer the subwoofer into the system design, rather than tack it on.
IMO, one of the important things about the RTA-12Bs is that the tweeter is up on top in its own little structure and set back the right distance to time align with the bass drivers. I've heard several Dahlquist speakers with this same configuration that are quite wonderful and would make great monitoring speakers. Of course, there's all those wonderful B&W speakers that have similar designs and are quite good and quite expensive.
I agree with Massive: accurate speakers are what you want. Ignore the labels and listen for accurate sound. You want full, flat frequency reponse, good transient response, minimal phase shift and linearity (no clipping or compression) over the whole frequency range all the way up to your maximum SPL. Good luck with whatever you pick!
Cheers,
Otto