they are both very good. Depends on your headphone. The D2 has strong internal amp while the fuze does not. D2 suffers from bass rolloff with low impedance headphones. Fuze is completely flat and does not suffer of such. However, if your headphones are full size and of high impedance, go with the D2. It is better. If you have an amp, the go with either. Both sound really good.
I own both, and for IEMs or phones with under 50 ohms impedance I suggest getting the Sansa Fuze. You do not have to worry about bass roll off with a Fuze and your Triple.Fi plus it really does sound great with no EQ settings on.
How come ppl feel the EQ on the Fuze is poor? Does using it badly distort the sound reproduction? Does ammending one frequency band (negatively) affect the reproduction of other frequencies? Is this including the various presets?