PS Stellar M700s for my subs? Do some Amp designs cut off low frequencies at 20 Hz?

I was thinking of replacing my Krell KSA150 amp that powers my two Mini-Marty 18inch B&C subwoofers (4 ohm version) with a pair of PS Audio Stellar M700s. As my mains have 2 ten inch woofers each, I only run the subs from about 35 to 16 Hz. The Krell at idle draws 7 amps continuously, wasting power and producing lots of heat. Am I missing something with a used pair of M700s? Class D is supposed to have great bass grip, the Steller produces 700 watts into 4 ohms, and will drive peaks down to 2 ohm. I'll admit using the subs for such a narrow band is overkill, but I built the subs for another speaker pair so I have them already. Has anyone heard the M700 on subs, or low frequencies? I'm sure there will be other amp suggestions, but I have around a 2000K budget for this. Thanks