Pete, have you read much on the evoM forum? Some guys that went 7670, a lot go "bugger it, I'm going 8374". The guys that go 8374 step up to the 9180. It's quite funny to watch.
If you want 400 KW and that's it a 7670 might be the go. But reaper on here is cracking gates at around 4300 RPM (from memory) on a stock engine (it does have the baby v cam), makes 470 kW using a 8374/1.05. You'll have a reasonably high comp 2.8.
Speaking to a few guys that have these things, the dyno graph doesn't give a true indication of how they drive. How soon are you going to make the decision?