As others have mentioned, your best bet is to try before you buy, especially since the basses you're interested in are all quite different.
My advice would be to have a look into second hand Warwicks (if you've tried one and like the feel), the second hand market for them is great for buyers at the moment and you can get a lot of bass for your money. Things like Streamer LX's and Thumb Bolt-Ons are often going for around £600 or less.
Something important to bare in mind with buying second hand Warwicks is the pre-1998 bolt on models have a much slimmer neck profile than the newer ones. Warwick used to use Wenge for the neck as well as the fretboards, now they only use wenge for the fretboard and they use ovangkol for the neck. I own both kinds of Warwicks, and whilst I have no problems with the neck profile of my newer model, the older Warwick I have is truly effortless to play.