I'd be a little leery of using a pre-amp, only because most modern HF radios, even portables, are fairly sensitive, and usually noise levels dominate at HF. A pre-amp will just amplify everything signals and noise, and add some more noise of it's own. Plus possibly some images and mixing products.
If you can get a sky loop type antenna up, I think you will see a dramatic improvement in reception. Since you have a 200' longwire now, I imagine you should have room for one that is a few hundred feet in perimeter? Another good choice would be a T2FD, although I think the sky loop would end up being easier to build, and probably work better.