Based on everything I've heard from people, the MEZZO are a real step up from the AVIANO's that replaced them. So, the Richer Sounds deal is pretty outstanding if you like the style of the speakers.
Another suggestion would be the Dali Concept series -
dali concept 6 - Google Search
Or the much larger more powerful Dali Concept 8 -
dali concept 8 - Google Search
If you really want some lethal speakers, consider the well out of your price range, Dali Concept 10 -
dali concept 10 - Google Search
Audio Affair is probably the best source for Dali Speakers.
At a tolerable discount, you could consider the Wharfedale Diamond 10.7 from Superfi.co.uk, who seem to currently have the best prices on Wharfedale -
SuperFi.co.uk - Wharfedale Diamond 10.7 floorstanding speaker
The equally good Diamond 10.6 (minus the midrange speaker, and slightly smaller cabinets) come it at about £499/pr.
SuperFi.co.uk - Wharfedale Diamond 10.6 Floorstanding Speaker
The new Monitor Audio BX5 and BX6 fall close to your price range -
Monitor Audio BX5 - Google Search
Monitor Audio BX6 - Google Search
Audio Affair also has a very nice price on the Acoustic Energy Aelite 3, which are a pretty sweet speaker, especially at this price -
Acoustic Energy Aelite 3 Three Speakers (Pair) at Audio Affair
That gives you quite a range of selections in your price range.
Which is best? Really, that is up to your ears, they are all good in their own way.
Personally, I confess that I like BIG speakers, so I gravitate toward the Dali Concept 8. But that's just me. Any of the speakers are going to be good, the real question is, which do you like and which can you afford.
Just a thought.
Steve/bluewizard