Speakers choices for AR REF-5/75s

You will probably enjoy a horn loaded/based speaker like the Avant Garde, Tannoy Canterburry or even the Zu Audio. They will sound much more lifelike and present.

Kalali-I listen to everything except what my 15 and 20 year olds listen to-dub and rap.

Pani-never considered horns. Like an irrational fear of clowns I guess. I will give them a listen.

What about hybrid electrostats like Martin-Logans? 

I have a pair of older Martin Logan Aerius i speakers driven by a yet older McIntosh MC2200 amplifier. Certainly not quite as refined as the ARs but I feel the speakers suck every ounce of (200wpc) power from the amp with the volume at moderately high levels. I think the 75wpc amp may be a little strained depending on your room size and listening habits. But amp aside, I personally find electrostatics sound an acquired taste. While they sound detailed and create a decent size soundstage, they have an extremely narrow listening sweet spot that can be annoying. Definitely try them first before you commit. With a solid foundation like the ARs, you have a lot of speaker options to choose from. I've heard your amp/preamp combo with a pair of larger and older stand mounted Aerials - not sure which model, maybe LR5, in a moderately sized room, and I was really (really) impressed. Definitely sweeter sounding than my set up.

Kalali- Appreciate your info. My current speakers have a narrow listening spot. It's a sweet spot but not everyone can sit their at the same time. 

So, after some research I purchased a pair of Audio Physic Virgo II.

A combination of what I think is an alloy tweeter and woofers located in the side of the cabinets is giving me the presence I wanted, without sacrificing staging.

Thanks for everyone's advice!