Best speakers, used, for around $1,000.

If you've been listening to Thiels, you've become accustomed to time-correct, phase-coherent speakers with first-order crossovers. The logical thing to do, then, is consider a couple of other manufacturers who also make speakers with the same design characteristics: Vandersteen and Meadowlark Audio. Vandersteen's 2CE is often available (used) for around $900-1000, and the same is true for Meadowlark's lowest-priced model. The Vandy 2CE is warmer sounding than your Thiels, and is a 3-way design and thus will usually have more bass response than the 2-way Meadowlark.

For what the Castle Howard's go for on the used market (due to lack of presence in the U.S.) I can recommend them as a fairly awesome speaker and an excellent buy. I had a pair in my system up until recently and really only replaced them due to an impulsive jump on a good deal. Very spacious and rich sound that's a pleasure to listen to.

Snell CV or Type D. Superb used buys.

Tannoy: System 12 DMT, System 12 DMT II, or System 1200.

Some who are used to speakers designed for domestic environments find the dynamics frightening, but it's worth it.

I'd have to second the Vandersteen suggestion. They represent a great value in the used market, as long as you don't mind the look. They don't look bad at all, but just aren't a beautiful piece of wood cabinetry, which is desirable for some. The sound is very neutral with good presentation thruoughout the entire range, and will not appear bright. My son likes to say that they don't sound like speakers - you just hear the music.

I just picked up Magnepan 2.7s for $1k on Audiogon and they sound amazing, even with an old Aragon 4004 MKII amp driving them. I think they would sound better with your setup. They're not bright but are very detailed and open. Bottom end is a little light but everything else is there. It's obviously a different type speaker with a different sound than your Thiels.

Try Thiel 3.5's. I sold mine 8 years ago for ProAcs but ended up missing them terribly.

There are many used magnepan 1.6QR speakers from $750-$1,100 on audiogon. If you can place them 3-4 feet from the rear wall and 8-12 feet apart they will give you the best bang for the buck unless you listen to heavy rock music. They like a lot of power so you need to see if your amp is sufficient. Take a listen at your local high end audio store if you can. They are more coherent and open than most box speakers at three times their price.