I own the E7 and E9 Amp and DAC combo from Fiio. it's 230 total (100 for the E7 which acts as a DAC and 130 for the E9 amp). it's quite decent. the the power in the E9 is way more than enough to power the grados. (I won a pair of RS2s).
I have heard that the DAC in the E7 is not great but I haven't compared it to anything else yet. I have ordered an HRT music streamer 2 DAC (150 dollars) and that is shipping now to replace the E7. I guess in 2 weeks I could give a review of the differences :)
I think, for the money, the E9 is a great, great amp. but you may want to check out reviews for the best combo units or standalone DACs.
aside from the searching you can do on on head-fi, here's a few links to headphonia reviews.
http://www.headfonia.com/category/source/desktop-source/
http://www.headfonia.com/the-new-recommendation-the-yulong-u100-usb-dac/
http://www.headfonia.com/fiio-e9-dekstop-amplifier/
http://www.headfonia.com/the-udac-2/
http://www.headfonia.com/the-hrt-music-streamer-ii-asynchronous-2496-for-149-95/