Surround Speaker Question

I would recommend Triangle Titus for surrounds. They are electrostat fast.
But there are many monitor sized speakers in your price range that will do a fine job.
Good luck.

Timbre is not critical for the surrounds. Fronts and center, yes.

As usual, there are going to be some that read to much into it. The OP wants a suggestion on surrounds without giving any info on the rest of his speakers.
Myself, I feel any good dynamic speaker that will convey background info will do in a normal HT setup.
If he was so critical, he would already know to buy the same brand and model as his fronts.

I must add that the BEST surround speaker would be the same speaker as the fronts.
But I gather that the op is looking for an alternative speaker that will work well.