Keep your stock saddle and get a bigger, cushier one as well. That way you can switch them around as you please. Maybe you'll like the larger saddle, maybe you'll like the stock saddle. Nashbar sells an Air Ride saddle for $25 which is currently marked down to $15. That's cheap enough that even if you hate the saddle you won't kick yourself for buying it.

I've read reviews that absolutely trashed the stock Jamis saddle but I've really grown to like it. I did buy the Nashbar Air Ride saddle which I plan to put on my winter beater bike. It's gotta be more comfortable than the monstrosity that's on the bike now and I figure for a 3 mile commute I can deal with the cushion.