I love the Yamaha sound. The filter, the envelopes just bounce and my SY-1 had the best portamento still that I've ever heard. I found it a pleasure to use and play with those CS/GX sliders and tabs. It was one of my first synths so I spent a lot of time with it.
I have the CS-80V and while it has the tone pretty much dead on, it just doesn't sound have the "sound." It doesn't sound like youre playing an analog synth obviously.
It is funny that you mention the T8. It is funny that during my crazy modular lust I almost sold it which would have been really dumb. I've been playing around with it a lot lately. So much so that I'm breaking it down. One voice chip is gone (again,) I've broken a couple of springs and the contacts are getting a little worn in the parts of the keyboard I focus on most. Luckily as far as springs and contacts go they are on each individual key and apparently are "easy" to replace. But yes, there's no reason to sell the T8 ever. I have plenty of modular now (1 case euro, 2 Serge panels, 2 full Modcan panels with a 3rd empty one, and of course the large modular I bought from Chile that I call my Moroder machine.)
The GAS has definitely died down. An old SY or CS would probably extinguish it. Just cruise the local ads now mostly. If I were to sell anything off it would be some monos. Have acquired a bunch again over the past couple of years locally.