Marantz 3300 - Fanboy issues, buyer beware.....

Consider portability and compatibility along with sound quality. Old gear is best left to tinkerers and collectors to source for themselves. You didn't say how old your son is, but if he is in the peripatetic years in his 20s, compact, easily-moved 2 channel monitors and a reasonable sub and a one-box integrated amp with dac and streamer would be a good option. JBLs SA750 is that, but maybe out of the budget range. Cambridge Audio CXA81 and a WiiM Pro streamer would be an excellent budget-conscious option.

@jetson  I'd say option #3.  He he...consider Schitt for higher end reasonable cost.  Watch Cheapaudioman on u-toob for many other budget but good options.  I feel like we're all thinking you're wanting to keep the cost down.

I would look into a used audiolab 6000a.

Has a competent phono, it has a streamer and it sounds great ( many great reviews)

Search in H-F shark basically new units for $500

Think so many people miss the point of vintage gear. Audio brings emotion. Marantz is as much art/decor as sound. Many people are building up system that attain a certain look, with sound being a byproduct. 

yes, lots of new things might sound better, but they look like poop. 

I would rather have a vintage Marantz for $600 then something new. Nothing sounds as good as my vintage setup for the price. Plus Marantz has a certain sound that some just love, much like Mcintosh.