I am considering selling my Warwick Thumb BO 4 - it is in near perfect condition. A question I have is this - I had a pro set-up/shielding job done by Mike Lull and he replaced the stock MEC pups/pre-amp (which I thought were junk) with Bartolini hum-canceling pups and pre-amp as well. In my opinion, the bass is better than a new one. Does making modifications like this tend to increase or decrease the resale value (I still have the stock electronics as well)? Is $1000 a fair price?