Loved the Koss Porta Pros and Sennheiser PX-100-II. I bought the ATH-M50, but I found the bass to be weak and lacking, even with EQ.
I listen to 192~320kbps MP3s straight out of my laptop and iPod. Looking for a something around $100-125, full-sized, closed headphones. Any ideas?
If you want loads of bass on the cheap the Sony XB series may be for you. The XB700 focuses more on deep rumbling bass while the XB500s focus more on punchy upper bass. Most people who like the 500s over the 700s only do so with major high quality EQing which your ipod can't do at all so the 700s may be a better choice. They like having more power behind them than either of your sources have though they are quite sensitive and will get plenty loud. They'll just sound better loud with a strong amp. They are a ported design and have good isolation and comfort though they do leak a bit of sound to the outside.
Despite these reservations, there isn't much else I know of that will have enough bass for you if you thought a EQed M50 was weak.