Recommend hiking boots for a guy who wears Birkenstocks

I wear Birkenstocks almost every day. This means, of course, that I have Birkenstock Duck Foot Syndrome. A friend of mine wants me to try hiking, so I’m starting to look around for hiking boots (about which I’m completely ignorant at the moment, unfortunately). I found that most standard boots I tried were too tight across the front of the foot, and if they were wide enough across the front, they tended to be loose at the back.

I’ve also tried on one pair of boots from the Footprints line of Birkenstocks, but I wasn’t really sure about how well they’d really work for hiking, since (a) they had a very firm footbed (if I’m going to be walking a lot, I prefer a shoe with a softer sole), and (b) they were deliberately loose at the heel, which I thought wasn’t recommended for hiking.

If anyone has any advice, I’d be most appreciative.