I was in the same position as you, looking for a headphone with a sound similar to the AD700, but more bass, and a fuller all-around sound. The AKG K701 was the one I've found to satisfy me the most. More bass depth, quantity, and quality, with a more neutral overall sound. Less harsh highs, but also more detail in every range. Also, an amazing soundstage that is at least as good as the AD700.
You will need an amp for these though, and they cost me about 250USD new. Well worth the money though, I believe.
I also have the DT990\250ohms Pros, and DT880\250 Pros. I find the DT880s to be fairly harsh at times, but everything I've thrown at the DT990 sounds pleasant. No more harsh than the K701, and definitely less harsh than the AD700 to my ears. The mids are entirely different compared to the AD700 though. Much more recessed. Same with the DT880\250s.
Also, I just got an amp in, the Matrix M-Stage. It definitely helped the low-frequency quality and quantity of all my headphones EXCEPT for the AD700. That one still sounds as thin as ever.