Designer underwear cost three times more than regular underwear. In most cases the only difference is the company's brand name is printed across the elastic band. Save your money and buy regular, comfortable underwear.
The only reason you might want to invest in designer underwear would be if you had a hot date and Calvin Klein underwear would help you close the deal. But then, don't forget to wear you baggy pants so that your date can see your CK underwear.