If you want to try a Brooks saddle, I'd advise going for a Brooks B17. And if you're concerned about having to go through several saddles before, get your saddle from Wallingford Bicycles:
http://www.wallbike.com/
From Wallingford Bicycles ...
"We guarantee you will be satisfied with your new leather saddle by giving a SIX MONTH UNCONDITIONAL GUARANTEE on all new saddles from Brooks and Berthoud."
So, you'll have 6 months to try the saddle and decide if it is going to work for you or not.
You should not need springs. A leather saddle has enough of a "spring" to it. Although note that if you go with a Brooks, when you take the saddle out of the box, it will be hard. Very hard. Worryingly hard. It will remain hard for the rest of its life. It should never be soft. But it is flexible and should conform to your butt.
You do not need a tractor seat. A tractor seat will cause other issues. You just need a saddle wide enough to support your sitbones.