So what kind of amp would be enough?
Dt-770's are 250 ohm and 100 mW and all the amps are usually displayed X mW to 32 ohm.
My $27 Fiio E6 on max volume can drive 250-Ohm Beyer headphones, so it does not take much to drive them.
It would help to know what sources your plugging the headphones into?
I bought the FiiO E6 just to test it out, you might want something better then the E6 for 250-Ohm headphones.
I know zero about the Samson S-Amp.