Apologies - I mistakenly assumed you were buying in bulk for students to use. Still, some colleges/unis here do have schemes that enable students to buy/lease at preferential rates, so worth checking out at the school/uni you will attend.
All I can suggest is that you go to a retailer, look at them in the hand, see how well built (and heavy) they are, and go from there. As I see it there are two choices - buy cheap and accept that it may not last forever, but that when it dies they'll be faster and cheaper, or spend loads, and hope it does you for four or so years. What ever you buy will feel slow and dated by then.