you probably just need to give the seat a little bit more ride time to get your butt used to the thing. Personally I love the stock saddles on my bikes. I have 2 Specialized BG saddles and some Bontrager thing on my Trek that is pretty decent. I've done many many 40-50 mile rides and a metric century on the stock Specialized saddles.

If you look at a human skeleton and look at the pelvis, you'll see 2 points sticking out where the butt should be. Those are your sit bones. If the back part of your saddle will properly support those points, then the saddle fits you. Too narrow, and you've got a torture device. Too wide is less of an issue, but most saddles that are too wide in the back are too wide in the front, and will rub the insides of your legs raw.

I don't know which store you bought your bikes at, but every store I've gone to in the city will help you fit your saddle and will likely take it back and have you pay the difference on a different one.