You are probably going to come out money ahead to buy a ready built bike and accessorize it to suit. Unfortunately when you the consumer buys parts they cost quite a bit more than when a manufacturer buys them, so you end up spending more money for an similar bike. However there is nothing quite like the satisfaction in knowing you built up the bike you are riding. I have built several over the years and they always seemed to ride better than the ones "off the shelf"
Aaron