Any chance you have 8, 10watt, 8.8ohm resistors kicking around. Using 4 resistors instead of 2 4.4ohm resistors might help power handling of the xo. Mind you, using 2 resistors is a bit of built in protection. As they heat up they'll resist more. And possibly burn up with enough power flowing through. Just be prepared to replace those for him if it happens.
The xo point is about 2200hz and the Vifa spec sheet says 50watts long term power handling. I would think pro use is long term power handling. But how much of a 100watt amp reaches the tweeter? Probably less than 50watts in typical use.
I'm not trying to scare you. Just offering advice. I would think you are in general ok here. Depending on his use. I'd just hate to see him take home his new toy and pump 200watts continuous rap through them at 120db and then something go pooofff.
Will he have a sub for these? The enclosure Q is a little on the high side. Bass extention won't be good. From Curt: "I still recommend using these
with a subwoofer, but they shouldn't disappoint if you don't". That was listening in his home. Depends how small is small, and what for of music.
Pro audio is a different beast
EDIT - Consider this http://www.parts-express.com/pe/show...umber=248-6700
Might be more than he needs. But has options and enough power to make these smoke.