pyrogen, once again what you say resonates deeply with me. I come from what I think sociologists call the X class. Both my parents were intellectual, college graduates, my mother came from a wealthy family. But they made the choice to go for low income but meaningful careers - working for social welfare, in non profits rather than private companies, stay at home parent, etc. And indeed I spent a lot of my younger years feeling like I didn't belong. We didn't have the money for me to have common hobbies with middle class kids, but couldn't find much common ground with working class kids.
I ended up piecing together my own network of friends with other outliers, mostly people who've had too bizarre experiences in life to fit the classical class/income system. Funnily enough, no matter how diverse the backgrounds, we often end up with similar attitudes: well read in social matters, science and fiction, environmentalists, internationalists, curious about the world, with an entrepreneurial spirit and political leftist leanings. Great mix
.
To address the original question, I too think that common experiences and attitudes in life count more than income - but then again the former make up a large part of what social class is. If you don't have these common references, however, you will be forced to address some daily issues through lots of honest communication, which is always a great habit for couples to take.