Unfortold "Carb Spacer" Power?

So the general assumption is that a decent mid-range priced spacer works wonders on a single plane manifold but it virtually pointless on a dual plane/high rise?

I have a stout 360 sporting an Edelbrock Performer RPM w/ a 750 Holley Double Pumper and am debating playing around with some cheapies to see if there really is any difference in performance let alone price...