E-street vs Promaxx vs 440 Source

For reference:
I sent a pair of iron heads to Brian at IMM to have him finish them and set them up for a .600 solid flat tappet cam . I supplied most of the new valves (I was short a few exhaust valves) and the heads already had new guides.
Brian did the valve job, new springs, retainers and keepers. The bill was $900, about what I expected.
I would have been borderline stupid/crazy to put that kind of money into 915/906/452 heads, but......
These were professionally ported max wedge heads that went over 300 cfm.
BTW, I voted for the promaxx. I have a pair of rpms and victors new in the box.