The load will be nominally half the power, but can step up to full power and then back to nominal often.

I plan to use an active PFC with an isolated DC/DC converter output. Instead of making one large power stage - I'm leaning towards building two converters and paralleling the output stages. Or making one AC/DC (PFC) stage and two DC/DC converters with paralleled output. I'm interested in the Intersil PFC chip (ISL6730). They have an app note for a 300 Watt PFC stage that I could implement and each of these run a 300 W DC/DC stage which would be connected in parallel.

I am also looking at Fairchild and TI PFC devices. I haven't decided on how to do the DC/DC stage. To parallel the outputs, TI and ST have parts for this.

Any comments or suggestions?