I have the same amp/speaker combination as you (well, almost - I have the RA04 which is essentially the same, minus the remote.)
I've experienced the same brightness you describe after a while of owning the 685s, once my ears had adjusted fully. I'd put it down to the nature of the aluminium tweaters.
However, I decided to have a go at tweaking, and I've now managed to achieve a much warmer sound, which is perfect for my ears.
Firstly, as you've mentioned, a decent set of stands with a fill helps a lot. I then upgraded my cheap give-away cable to some of this stuff: http://www.audiovisualonline.co.uk/dynamic/eshop_products.set/ref/47/profigold-pgc7254-bass-reflex-speaker-cable/display.html
I decided to bi-wire with this cable and it really did make a difference - whether that was the cable itself or the bi-wiring, I don't know, but the resulting sound was much warmer and to my taste.
Just my experience.