NAD C326BEE or C355BEE.
I've just returned a loan pair of 685s after trying them at home for a few days, and they performed very well with my C325BEE. I had previously heard the 685s with a Marantz PM6002 and hated them, so it was interesting to hear how different they sounded on the end of the NAD. With my amp the 685s sounded very detailed and well balanced with no excess flab in the bass and no harshness in the treble. The fluid midrange of the NAD amplification also helps to counter the slightly recessed character of the 685s midrange so that voices have decent presence. With the Marantz they had sounded splashy at the top end and slow in the bass, which perhaps goes to show how revealing the 685s are of the electronics.
Ultimately the 685s still aren't for me. They are a bit dark sounding for my tastes and slightly on the safe side, but excellent speakers and talented all-rounders. Talking to my dealer colleagues, the next incoming stock is July so probably worth getting your name down on the list sooner rather than later!!
Apart from NAD, I'd also suggest trying a Rotel RA-04. If your budget is larger than that, then the Creek Evolution or the Roksan K2 are the stand-out products in the next bracket up. I also love the Naim Nait 5i (probably more than any other amp under £1k) but I'm not sure it would make a good match with the speakers.
Also worth trying the Rega Brio 3. Great value for money and capable of a very musical and spacious sound.