The first speakers that come to mind would be Thiel CS.5's. Granted, you may want to add a nice subwoofer later on, but I love the accuracy and imaging of these little Thiels. With a good sub, they can compete with setups costing much more. If you bought new, I would think that NHT would be strong in that price range. Some other used contenders might include Meadowlark Swifts, the smaller Totem floorstanders, or maybe even ProAc (which would pair up well with your Arcam).
Tom.
Tom.