For $400 and you'll use an iPod, you won't need the DAC, unless you'll be using it also with your laptop. That said try the SR225i and the NuForce Icon Mobile, and don't forget a decent LOD. A tip though: by "decent," forget those heavy-duty exotic LODs because the mini-plug will be too fat considering the slim profile on the Icon Mobile, which complicates things if it's stuck on the back of the iPod. The Fiio LOD would work well enough. If you won't use it with your laptop or desktop PC, might as well get a decent CMOY amp.
And if you upgrade sources down the line, or build a full system at home with a disc player or your PC as source, I recommend you listen to the SR225i with a DAC-AH/Valab DAC and a decent tube amp. Pop in Pantera's "Cemetery Gates," Metallica's "Wherever I May Roam," Therion's "Nightside of Eden," Epica's "Facade of Reality" and "Consign to Oblivion," just to get started. Cured me of upgraditis, other than the need for a K70x for the amazing separation and extended treble with Epica.
Just one issue though: the noise WILL be a problem, I rarely listen to my Grados out of the house. Maybe in coffee shops but since I smoke, I usually sit outside unless it's too darned hot. Best probably is to build a full system at home around the Grados and stick to IEMs when out.