What benefit are you looking for by spending the $$'s for an aftermarket intake? Studies have been done to show that you do not gain hp or mpg w/ an aftermarket intake (until you add other mods).
Here is one study worth looking at. Yes, this study was using an AC Delco filter, but the Ford Donaldson air filter is even better than the AC Delco. The comparison holds true. I have also read articles on measured hp that show no real world gains. I have yet to see anyone w/ a stock truck post statistically valid numbers showing a benefit from aftermarket air filters. There are much better mods to spend $$'s on than this (unless you like the looks of some RAM AIR style intakes OR the ease of filter change).
Powerstroke Mods and Maintenance
Some additional reading (hope the links are working):
K&N why so bad? - Ford Truck Enthusiasts Forums
Best Cold-Air Intake Brand for 6.0? - Page 2 - Ford Truck Enthusiasts Forums