I really feel for you ... what a rotten situation and it's great you're being proactive ... so please don't take this as a criticism ... but if your main reason for leaving your current job for a new employer is for a higher salary, it will come out in the interview if you get an interviewer with any level of perception, no matter what you say.
What I think would help you the most is to really focus on what you want out of your career, rather than how to describe why you are leaving. There are any number of books that can help you do this, and you may already have done it.
The advantage of focusing on what you want to do is that you will either discover you are in the right place already (probably not), or you will have big-picture reason for why you want the new job. For instance, you may discover that you can only reach some particular goal by joining the new organization. Then the answer to the "why are you leaving" question becomes "this is what I want from my career, and your organization is the right place because ... and this is what I can do for you if you hire me."
People who are "leaving of" a place come off differently from people who are "drawn to" a place in an interview. People who are truly seeking new opportunities that fit the job opening are easily recognized and much more likely to get the job. It is a matter of attitude. I am regularly involved in a few permanent hires and internship decisions, maybe half a dozen a year, as primary hiring manager for positions from student interns to senior scientists who will work in my lab, but also have been involved at all levels, even up to the CEO level. People who try to snow a good interviewer who really cares about the position they are trying to fill are normally easy to spot and do not get an offer. We have very low turnover in high turnover field, in part because of the care we take in filling slots. That's including before the downturn.
Not saying all interviewers are going to be perceptive or care, of course! Many will be rotten. But hopefully your new position will be with a company that cares, and such companies will be more apt to hire you if you're truly passionate about what you can do with/for them.