klipshorn speakers

I heard a big Mac solid state amp feeding high efficiency speakers and it was a terrible sounding combination.  At any reasonable listening level the sound was lifeless and unengaging.  With high efficiency speakers you don't need much power, you need something that delivers great sound at fractions of a watt output.  Look at low-powered tube amps, most of the best sounding amps I've heard have rated power output under 40 watts.  I don't think the tube Mac amp--275 is the answer either; I heard that in a high efficiency system and it was also pretty bad sounding (also lifeless).

I don't think you need 40 watts, but, the Synthesis A40 is a terrific sounding integrated amplifier (it includes a very good DAC) that would fit the bill.  

I presume the linestage portion of the 7300 would be used with the new amp, if that is the route your son would be going.  It is possible that the 602 is better than the power amplifier section of the 7300 such that there will be an improvement in sound.  But, I suspect that any such improvement will be extremely small.  The difference between ANY higher end solid state amps is quite small, and in this particular case, the difference in power is completely irrelevant because so little power will ever be used by that speaker.  If you want a substantial improvement in sound, look to getting a good tube amplifier.  If it must be a Mac, then consider the much older offerings of that company, such as the MC 225 mentioned above or an MC 240.  Neither looks as pretty as current Mac amps, but, they sound pretty good and will be appreciated by the hardcore Mac fans who know their favorite brand.