Good match for Rega Brio-R

A used pair of Harbeth P3ESRs can be had for $1700.  A book shelf that is tough to beat for the money.

 We have run the Rega Brio/Vandersteen 1CI successfully paired together at Audio Connection for years.
An easy 90 DB efficiency 6 ohm provides a safe easy load .
In my opinion its advantage is a more open sounding experience with a dimensional feel.
When compared to mentioned box speakers above i think you'll find its tonal and imaging abilities well beyond exceptions.
The 1CI features a unique multi enclosure that many more sophisticated designs use yet at working mans pricing. Their phase and time correct drivers, that get the whole timing of the music when compared to other conventional wisdom box speakers.
The 38HZ bass extension just makes music more full and natural.
This speaker also comes with a well written easy to understand  owners manual guiding you to the genuine performance of what you deserve.
 Here is a review.
http://www.tonepublications.com/review/vandersteen-1ci-loudspeakers/
JohnnyR
Vandersteen dealer

http://www.tonepublications.com/review/vandersteen-1ci-loudspeakers/

IMO, your going about it the wrong way.  Usually one get the speakers first, as they are the only component you can actually hear, and then one finds a suitable amplifier to properly drive them.

But it seems you already have the Brio and are locked into it.  So I suggest you understand it's output capabilities and then find speakers that have the proper specs (impedance & sensitive) that the Brio can meet without breaking a sweat.  And by all means, audition the speakers to find the pair that sounds best to you, your amp can properly drive and are within your budget.

The Rega is not a powerhouse at 73 wpc in 4 ohms and there is even a warning on their website to be careful driving 4 ohm loads.  I would take this to heart and stick with 8 ohm speakers within sensitivity ratings at 90dB and above and you research and develop your short list.  Your Brio will be much happier.