The Mad Dogs look like excellent headphones, but I don't think they are a good choice for using with no amp as the OP will. Correct me if I'm wrong though.
Fiio E07K and E10 are the go-to recommendations for inexpensive DAC/amp combo units, but IDK how well either would work with the Mad Dogs.
True. I think, like a lot of headphones, it's better to say that they scale VERY well with an amp. But as a first venture into this, it might be better to go with a different set of headphones, or maybe $200 'phones + $100 amp > $300 'phones.