there is a considerable difference between the ex and si. i have and si and my wife has and ex, both 2000. i think it all depends what kind of money you are looking at spending. to add the amount of power to really feel a difference is not cheap to me, depending on what cheap is to you. i have a few bolt on and still saving for a turbo/supercharger, but i really wish i just done a swap and got a gsr or if really wanted to drop a dime the new k20 out of the rsx.