Democrats--Define for Me "Middle Class"

I had an interesting conversation with a Democratic friend of mine this morning who was complaining (already) the the Bush plan to tie Social Security Beneifts to income was going to harm the middle class. Bush's Social Security plan now includes a means test, which just makes sense.

So here is the question I asked of my friend (whom I love dearly and love to argue with dearly). Define for me "middle class?" After a little hesitation, she declared herself middle class. When I pointed out that the salary she and her husband pull down together (approaching $250,000 per year) put her solidly in the top 5% of all income based on 2003 Census Data, she paused. By the way, if that is middle class, sign me up. I could pay off my student loans, my house and my credit card bills.

So that is my question to all Democrats, "How do you define middle class?" I need specifics. I need an income range for a household. If the bottom limit is $30,000, what is the upper limit? I need details ladies and gentlemen, not rhetoric.