Talking about ear buds, you can put together this very nice system:
G-Lite > Pico Dac > Yuin PK1
This would beat many, many headphone based systems. Of course Boomana's is a great approach if you insist on headphones:
G-Lite > Pico Dac > Grado HF2
If you must base your system around the K701, you'll have to spend enough money to get a good amp that can give them the current and voltage they need to sound their best.