Just checked that Topping DAC and Amp combo, has 4 days left.
It would work for your Senns.
They are 300 ohm cans, and I have heard mine on the Topping,(the one I reviewed here), and they are powered fairly well.
You should, however, visit the JDS Labs site, see that what they want for the O2 DAC/Amp combo in the "B" stock section,(minor blems, new gear), is only $239, VERY NICE equipment.
You will not go wrong with the JDS power and sound...