Rookie looking amp/receiver advice

I am attempting to put a decent "quality" system together for my son. I have about $500 left to spend. Currently have him a set of Monitor Audio BR2's for his mains. This will be his personal stereo for his dorm/room only for the next 4 years as he is headed to college in September.
I currently have BR2's hooked up to my old Yamaha RX-V495 receiver and an old Sony CD player. My question is would I see a big improvement in sound quality with a decent amp/receiver? Or is my Yamaha adequate?
My overall question is what direction would you take at this point with the money I have left to spend? Thanks in advance for your help!

Does he listen to or need surround sound?
If not what about an inexpensive but durable integrated amp.
Just another way to look at things.
I would put the money into a headphone amp and a pair of headphones. They just may come in handy.
No need for surround at this point. This will stay in his dorm and room in his apartment. When he moves to an apt or house next year I will get him a decent 5 channel receiver and a big ole set of cerwin vegas or something similar. That way if they get damaged its not a huge deal.

He has a set of bose headphones he uses with his laptop/iphone. Those should be ok for him for now.

What amp would you look at to run those speakers? From what I have found seems as if an older used Rotel amp/tuner may be a good option? I will add a powered sub at some point.

Would it be wise to look at a good receiver?