It's still a pretty good amp combination but a lot will depend on what you are feeding it with. There is some serious competition available depending on how much you want to spend, Lehmann Linear D offer a superb combination amp/DAC, Simaudio Moon 230 HAD will set you back £1500. As will a Naim DAC V1. Looking at those prices the Marantz looks something of a bargain.
The headphone section on the Marantz is the same, with more power, that is fitted to their amps and CD players, I have an sa8005 and cd6006. Although they are pretty good, especially with low ohm high sensitivity 'phones they are easily outclassed by the likes of the Lehmann Linear, especially for those 'phones that like a bit of power, such as the 660s.
Is it still a good amp, answer has to be yes.