I bought my JD Thumb in 1987 for £900 (I think my somewhat battered 70s Precision had cost me £125 a year earlier). It was a huge amount of money but once I played that neck, I was hooked. I still haven't encountered a better (to my hands) 4-string neck. The later Thumbs I wouldn't bother with (haven't tried the most recent slimmed down ones yet though, but £2650 for a 5-string that is rather more mass-produced than my old Thumb seems rather costly) - I did buy a 2000 Thumb but had it defretted and the neck reprofiled to the same dimensions as the JD Thumb. I wouldn't say the early Thumb neck was either C or D, it's (|.
I've played quite a few Spectors and would like to get on with them because it seems to me you can get some bargains, but I just don't like that thick neck. And the most important thing about a bass to me is the neck.