Were I in your position, before a new DAC I would look into amplifier(s) better suited to the Maggies 3.6.
I'm a fan of Classé amps. I own a pair of Classé monoblocks which I love. But the CAP-151 was in a different product category, and it's doubtful it can deliver the kind of current big Maggies crave. I would expect a pair of big-iron monoblocks to deliver sound quality improvement far beyond anything in the digital chain.