IMHO I would run the CPI's on your setup. T-5 are a great pipe and run awesome, I just prefer the CPI...everyone will have their own opinion on pipe choice though.
You should be able to beat most 450's just from your current setup.
If you want some more power, hit up a site sponsor and look into getting a 4mil crank. If you want the best bang for the buck IMO get the new serval cylinders.