Ask Engadget: What are the best headphones to use with the iPod?

Alright, this week's Ask Engadget reader question comes from Peter A. who asks:

What are the best headphones for my iPod? I bought the upgrade headphones from Apple, they sound great, it's just
that I have to keep pushing them in to get any bass. Needless to say, I am getting pretty tired of doing that...so what
should I get instead?

We're big on the Sennheisers we picked up last year, but what would you guys recommend?