I will say, the Q701 is a lot more natural sounding. In direct comparison, the Q701 is easily the better can in everything but speed and bass. I was quite disappointed in the Pro 2900 when directly comparing the two, which was my fault. They don't sound remotely alike, and I felt they shouldn't be compared in that way. A better comparison would be the 880/990 and HE-4.
Based off the Pro 2900s own performance, not comparing it to anything, and understanding that its bright with a V shaped sound curve, the Pro 2900 is very enjoyable and a fantastic headphone, just overpriced, IMHO.
Personally, I don't think you'd like it. The Q701 has spoiled me too, and the difference is why I didn't put a direct comparison in the review.