iv not read the thread, too long, but il give one piece of advice. Forget that you have 4000 to spend. Dont go out there looking for the most expensive bass out there thinking that it will be the best you can buy, it most likely wont be. I would never even consider spending anything more than a quarter of that money on anything but a custom build by a damned experienced and accredited luthier.
Try basses at the lower end of your budget. Every bass is unique, you may find a bass for £1000 that suits you more than a £4000 custom. Bare that in mind, and good luck!