High End Quality Retailers in the Chicago, Il Area

You should point him to this website for education, and to save money. Have him read, if he truely has an interest he can learn many valuable things...and the savings is both in buying used and buying the right gear the first time.
The trouble with pointing a newbee in the direction of a dealer is the potential attitude that rub many novice's the wrong way and the high prices, if any of these 2 issues happen to bother your nephew you may never get a second chance to have him explore this hobby.

There is http://davincimedia.com/ just north in Milwaukee. Not far if he lives in the north burbs. http://www.saturdayaudio.com/ in Chicago itself. The is also http://www.abtelectronics.com/ in Morton Grove, they have some entry level stuff and do superb custom mobile audio. Dennis Rodman had one of his autos done there as well as a few other big guys. Thats just a few. And there was my house but I don't live around Chicago anymore.

The best place to go for fun and a solid education is Quintessenceaudio in Morton Grove. Not far from downtown.
Give Mick Surrvance a call.
847-966-4434
I think after speaking with him you will see why I recommend him.
Your nephew will have a blast and learn the what, why and how in developing
his own personal tastes. You are a really cool uncle by the way. Nice job man.
This is where I send relatives and friends. The first part of Chandliz's post is quite solid. Reading is a good thing, hearing and seeing are equally important.
Creating relationships and learning from different council, good or bad, is part of life.
The choices we make are what defines us as adults

I agree establishing a relationship is key in this hobby, I just know from seeing the poor victems who go to these stores get a dose of arogance and rudeness quickly turning their feet towards the door. my main point was learn enough about what you want to not let that crap get to you.

All good points. That's why I suggested music direct. They are great to work with and don't push any single product. They have a huge selection in all price ranges that you can actually go see. You can look at everything on their web site first and do research here.

Once you have all of that knowledge and experience you will be ready to buy, be it new or used. I don't know of anywhere else in the area that has the variety they do. Good luck!

P.S. I have no affiliation with music direct what so ever. I have just had great service from them.