Newbie question - dedicated headphone amp or is my McIntosh MA352 sufficient

Not sure if your phones and amp are a good impedance match, the specs don't say. Try it first, the Mac headphone amp should be good enough. 

Headphone amps in integrateds are usually a bit of an afterthought, and McIntosh doesn’t specify the headphone power output of your amp in the specs, which would lead me to believe it’s nothing special — could be wrong though.  The HE1000s do require some power to get the most out of them, and frankly I think a $3000 pair of headphones deserves and will greatly reward you for a better headphone amp.  Just my $0.02 FWIW. 

agree with soix