Thanks @rem736. Confirms what I found. You clearly get what you pay for with the Sony. Bigger, better, stronger, faster (and lighter) (cue Daft Punk).
Definitely going to get the SDP-S1 but the price to ship to the UK is just holding me back at the moment. $800 from Sony direct vs $1100 from shopereaders.com (+ shipping).
But I have been waiting for something like this for years...