Got the Sigma 18-35 f/1.8 today. Haven't had time to play with it much but it is very solid and sexy. Seems to focus pretty well and is pretty quiet. Also, the zoom ring is so smooth.
I also love the Peak/Volcano + HD800 combo. I am sure that I probably mentioned this before. You can't really go wrong with the GS-X though and the new ECP Audio Black Diamond sounds very interesting.
^Why don't you get another RS-1? I know you loved that can. Either that or get the PS500. I would personally stay away from the HiFiman stuff but that is just me.
I love the HP 18 and will probably buy another bottle every time I run out. Have you had Talisker 18 Stretch? It isn't really like the HP but it is fantastic - one of my favorites!