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!

blandis
With the new models coming out, a older Rega Brio might be a good solution. Price should be in the range. No remote, but also pretty well bulletproof and 50Wpc is plenty for a dorm. A nice stepping stone to better hi-fi after college too.
His generation is tied to PC's for music. Get him something like an idecco with a USB input to stream music. Radio means nothing, what kids even use cd's?

Spend an extra $75 on a back up hard drive for his pc as well. That could save his life, grades, career and more...