recommendations for replacing parts?

I recently had my front tire, seat and seat-post stolen from my bike while at school (I'm in college). I would like to get a good, light-weight wheel and a sleek yet comfortable seat without breaking the bank. There are so many choices I don't know where to start.

I want good-quality parts but I don't want super expensive ones as I'm afraid someone might try stealing those off my bike again. When I found my bike, there were still 7-8 other bikes next to it but they all seemed in tact. Some of them were newer looking than mine- mine's a used Bianchi Sport SX. I had just replaced the front tire with a Gatorskin since I'd been getting too many flats prior. And the seat, while I'm uncertain what brand or style it was (it came with the bike when I bought it from its prior owner and I never bothered to pay heed to it), was a slender light-weight road seat. Those were probably the only nice things on my bike.

Any recommendations/reviews for a wheel, tire and/or seat would be greatly appreciated! My wheel was a 700 x 23 and the seat post, according to sheldonbrown.com is 26.6mm