Your information is incorrect. The 3800 Pro edition comes with a Colorburst RIP, not the RIP from Colorbytes. It also comes with Postscript.
The Colorburts RIP can use any ICC/ICM profile.
Whether one needs the Pro edition of this printer comes down to whether one needs Postcript printing capability and a RIP. The price is certainly right, if one does.
I am not familar with the Colorburst RIP so I don't know the extent to which they do their own "screening". If they do then there might be an improvement in image quality, though if there is it will likely be quite small.