Need Help buying headphones and head amps

My nephew is looking for quality headphones and a head amplifier for listening from his MAC computer. I know very little about headphones and head amps so I need some recommendations. After some research, I found the Sennheiser HD 650 Headphones and also the Grado GH1 headphones. The IFI - MICRO IDSD DAC also looks very interesting but I do no know. He will probably run a USB cable from the MAC to the head amp (any other suggestions?).

Does anyone have any suggestions for a high quality headphone and a head amplifier? Let’s assume a budget of $1,000 or less for both items. Any suggestions would be appreciated.

My plan is to give him 2-3 suggestions for each item and will then suggest he visit a dealer for listening and additional help. Where should he go in the downtown Chicago area for assistance? He needs a dealer that will help him make these decisions. Of course, purchasing items on line is also an option if someone suggests something. Thanks..
Take a look at the Topping TP32ex. You can find them on Amazon. It has a
good Dac, USB input, plus a digital coax and analog input as well. It is not
only a headphone amp, but is also a 50 watt per side digital power amp to
drive speakers if so desired. I have it and it sounds great.
in chicago/evanston/hinsdale audio consultants would be a good place to audition heapdphones and amps--they have alot of grado and sennheiser at different price ranges
Head Fi is a great source of information but is a bit overwhelming, there is a lot of info out there. It takes a while to get used to it and also the tenor of the conversations which tend to be a younger age centric- than what you encounter on Agon.
What's hot right now is a tube amp from a company called Garage1217, the model is called a Project Ember. It has a feature that is not seen with speaker amps, in that you can roll almost any tube you want in it.
I have been using Sennheiser HD700s for headphones and can recommend them to my generation of speaker listeners. They are well balanced, but younger people seem to crave more pronounced bass, making the HD 650s popular.
The advice promoting auditioning is always sound. The Ember and the street price for HD700s comes in under a grand but just barely. Also there is no DAC with this set up.