I bought my Ultrasone pro2900 last year on Amazon when it was $384.
Before I hit the old classic iPod 4th gen monochrome clickerwheel, I have been through iPhone 4S, Schiit Audio Asgard(amp), Audio-GD NFB 5.32(DAC-AMP), Little-Dot DP_I(portable player), the Acoustic Research AR-M1($830 portable DAP).
After all these tries, I have decided that the old iPod is the best of all. My pro2900 under the old 20 gig iPod had the most balanced low, mid, high freq respons, best sound-stage(so far) positioning and shape. The most important thing to me is that under the old iPod, my 2900 doesn't sound overly bright and stimulating anymore. If you feel like listening to this combination for hours and on, you won't end up with a pair of buzzing ears.
The only problem with the old iPod is that they are almost 10 years old so that their battery and 1.8 inch hard drives might fall apart anytime. However, this can be dealt with an ATA to CF converter easily available on eBay and Amazon. Also, 32 gig CF cards are also pretty cheap right now. The replacement batteries cost as low as 3 bucks.
Anyways, I suggest you guys with the pro 2900s to give the old 4th gen iPod a try. It won't disappoint you.
Edited by Audiofail - 11/28/13 at 2:41am