You sound like you've lost your love for the cotis. Interestingly, I was just thinking of you today. I recently got a 4x2 Genuine Belgian Coti similar to the one you had a few years back. I've been waiting a really long time to find one like it, and I touched up a Union Cutlery Co on it that I'd previously finished on my Barbers Delight and it was possibly the most beautiful shave I've ever had. It was definitely cutting at a higher level than 8k, but I wouldn't say as sharp as a SS12.
Interesting to compare thoughts in this thread with your statement about the Salm coti:
http://straightrazorpalace.com/hones...coticules.html
Also of interest is Bart's comments re. Capt Zero in post 22 here:
http://straightrazorpalace.com/honin...tml#post251465
Back to the OP, if I were you, I'd follow my old mother's timeless advice, 'why buy one when you can buy both!'
And if I were starting all over again, I would buy a good synthetic progression, and a nice Thurrie, then after a year or two of experience with that I'd buy a new coti and and crazy expensive labeled vintage one. That way you'd always be able to put a great edge on your razors but still be able to play around with things.