In my experience of the Ref 2, original ones, buy a good quality power amp asap.
They will be relatively dull and lifeless until you feed them something better.
£900. Difficult to say. For starters, someone mentioned that there are Parasound 1205's (it'd allow biamping) available for £1K for a little while. A start at least.
One dealer that had/used to do that deal is www.signals.demon.co.uk They could certainly suggest an alternative.