Help Selecting 2x75W Board for 24VDC Supply (or something)

Hi, I'm working on a box that has a Dayton KABD-250 running things, which likes 24VDC 5A. I need to add two more-powerful channels, >/=70W RMS into 6Ω, whatever that translates to in chip amp marketing specs. HF performance is not needed, LF is. So... how do I pick a good board or kit for the extra channels? Looks like I could get a 15A 24VDC supply and try to find a 24VDC amp, but most the higher output ones seem to want 40V+? Should I use a higher voltage supply and and drop it to 24 for the Dayton board with a transformer?

I'm a speaker guy, not great at this stuff. Thanks in advance for anyone willing to give suggestions.