I've heard the Syren several times. I own a TRON Meteor, which was the immediate pre-cursor of the Syren. In fact, my Meteor is Graham Tricker's (TRON designer) personal demo unit which was upgraded over time to use circuits very similar to the Syren. Mine is silver wired throughout and has WBT connectors.
What can I say? It absolutely is NOT bright at all. The 6moons review is pretty much on the money - not hyped up or overplayed. My Meteor sounds fabulous and the build quality is awesome. You will not find a better quality build anywhere. What's more, all the Syrens are built by Graham himself, as is all his kit. No outsourcing to a cheap far eastern factory.
I would email Graham himself (email@example.com) or call him +44 1895 833099. You will not find a nicer guy to talk to in the hi-fi industry. He will answer calls until about 10pm UK time as well and often at the weekends too.
Jeff at Highwater is his US agent and Graham would want the sale to go through him (as he's pretty honourable about these things). In the past, he would consider selling his amps to overseas customers on a sale or return basis - he was that confident about his product. I'm not sure that he can still do that now. Also if you want to use a particular phono cartridge, then tell him and he will build the correct loading in.
I've known Graham for over 15 years now, but only as a loyal customer. I have no other connection than to say how happy I've been with his products and more importantly his after-sales service.
I hope that helps.