I think that I would go for a used pair of ADS "large" bookshelfs in your situation. There are many two way models that were made from the 70's into the 80's, just make sure that they have rubber surrounds. The three way models are more expensive, but worth it, and I am not usualy a fan of moderately priced three ways. I had a pair of 710 (three ways) in the 70's that sell for more now than I paid for them used 25 years ago. They have plentiful bass and a good balanced sound for "all" types of music should your nephew branch out. They are also easy to power.
Used speakers
I've recently upgraded and am giving my nephew my ancient Hafler 220A amp and Hafler pre-amp. The amp is rated at 120wpc. As befits a 16 year-old, he likes his music loud with lots of bass. I'd like to get him some used speakers in the $250 range. Any suggestions, biggest bang for the buck? Do I need to spend more?