The crank you linked to is the new X-drive version so you don't need an ISIS bb. With that in mind DON'T buy an ISIS crankset, ISIS bbs are the pits.
What do you mean by competitive? Are you racing? If so and you don't weigh more than, say, 190lbs I'd look into lighter rims than rhinos.
Also, upgrading a bike is a lot more expensive than buying a new one in the long run. Here's a realy nice bike for a racer on a tight budget: 2005 Kona Caldera
although it has one of those pesky ISIS cranks.
By the time you add up all your upgrades I bet you're at 1/2 the price of the new Kona, and if you buy the new Kona you have a good backup bike for commuting!