i'm about as far from the office world as you can get, but i wear dickies almost exclusively. they are obviously perfect for the kind of work i do, but on the rare occasion that i need to look a little bit nicer, they do the job too. they don't wrinkle, and as long as they are clean and not faded, they work as basic slacks too.
i've never tried to get away with them with a coat of any kind, but have definitely pulled off shirt and tie, or a nice buttonup with a mandarin collar. cheap, too. they might be too casual for your work, but any time i wear anything other than a t shirt or jersey with them, i get complimented. maybe my friends just have low standards for me.
my other "dress up" option may or may not work for you, depending on your confidence, how liberal your office is, and whether or not you have nice legs. i have a couple of kilts that dress up pretty well. not for everyone, but they sure as hell aren't slacks.
www.utilikilts.com has styles that vary in dressiness.
