Well this is something to think of - a few points actually.
The fact that they CAN play down to 150hz does not mean they do that well and as well they need an enclosure of about 0.3cf in order to do so.
Most people are saying that they excell as a midrange starting at 500hz until 4Khz or so.
The diamater of this element is very small and in most cases a 6.5 inch would perform much better up to 800hz than the ES02.
Take as well in mind more things such as:
1. up to 800hz directivity is not an issue and you can easily make your 6.5 midbass sound as if they are playing up on the dash height instead of the floor level.
They will "connect" or interact seamlessley with the CDT ES02
2. Most 6.5 inch drivers would steal not be beaming up to 2khz (thanks Andy).
So why put so much stress on the CDTs form the first place if the Imagine would do it better?
I noticed in my case that they do not sound well below 900hz but that is also much to do with the tiny enclosure they are located in, I believe that in a more roomy space they could as well sound well at 500-600 hz but really up to 700-800hz I really do not see a reason why not to let it come from the midbasses in the doors.