I also got the d7000 recently and I tried them on a few setups at my friends and head fi meets. I've been trying to find some good cheap setups for my cans ever since my DAC fried. So I began my quest to search for a good temporary setup so I can save up money for something like a Burson 160D (which sounds amazing with the d7000 btw).
The e7/e9 combo works pretty well but I preferred my setup (just a modded asus essence STX) over it. Some of the detail is lost but it is definitely sufficient enough to drive d7000. Hell, the d7000 drives way better than the k701 or ad2k I own through my laptop 3.5mm jack. My favorite part with this combo is the fact that you can use the e7/e9 separately. Definitely a solid choice if you want that extra portability.
I would recommend the STX but it is not portable at all. Great performance for the money. But sometimes I do wish I got a more portable setup since I do travel with my laptop a lot.
I had a chance to listen to the nuForce Icon HDP not too long ago. Impressive! Brings out the mids for the D7000 and tightens the bass. It feels like a perfect match. Having a preamp is like icing on the cake. The cons? They are not as impressive with the k701, but still great. Another con are they are slightly over $400 and not as portable.
The audio gd's sparrow was another amp/dac I had a chance to try out. Hmmm, its better than on board sound but I really didn't see a reason to get a sparrow especially with all of other cheap options in the market now. Just another combo you can research for yourself.
Last but not least, the nuforce udac2 + JDS o2 amp. I had some time with this combo and I was not disappointed. I can't really comment on the nuforce udac2 as much except for it gets the job done with really clear sound. But the O2 is amazing. Highly recommended for the d7000. My favorite part about this amp is the BASS. But I'm no reviewer, just go look it up.
Here's some suggestions that I just threw out. I'm sure no matter what you get in the end, you will be happy with your purchase. The d7000 benefits with a good amp and dac, but I haven't really found a setup that was bad with them. They are no where near as picky as my k701s. I even got to try out some tube amps with the denons. They are the only amps that I will not recommend getting but it was definitely not too bad!
Good luck with your amp/dac hunt!