I think you need to narrow down your requirements/wishes first. You are looking for a field recorder, but you'll consider a computer with an interface, too. That's a very long list of options you're opening up here.
Even with regards to the field recorder you've only said better than your Zoom, but cheaper than 2500,-. Still a long list of many very different devices.
Once you've narrowed it down a bit, perhaps then someone can help you with the choice.