I think this misstates the question.
First, the question of imperialism is first of all the question of the imperialism of the chief hegemons -- usually at least two up to WWII, but currently one. (This is _not_ a matter of moral judgment of different ruling classes. They are all more or less equal slimeballs.) Given the existence of such a "core" imperialism the existence of several or many sub-imperialisms is strictly derivative. (The rhetoric in Germany of "a place in the sun" was not merely greed & power hunger on the part of German leaders.)
And the phrase "first world capitalism" (ignoring the balance of actually existing imperial forces) carries at least a suggestion of "first world affluence." (And other posts do express it in terms of "first world [period]" rather than "first world capitalism.")
I think it very nearly self-evident that (in physical terms) first-world affluence could be maintained without exploitation of the third world. It is not by any means evident that the first-world _capitalism_ can maintain itself (or even _think_ about maintaining itself) without its imperial power over the third world. But this could be the case even if we were able to demonstrate that imperialism _reduced_ rather than increased profits, _damaged_ rather than improved "first world" material wealth, etc. At some point in the argument those statistics become important, but it simply bizarre to begin the argument with an exchange of this sort.
Next, "super-exploitation" is probably a false concept, since I really don't see how it can (for the most part) be defined except in moralistic terms. It is a sheer whimsy, an emotional response, that tries to differentiate super-exploitation from exploitation. Hence I think it a serious mistake on the part of Charles, Michael, et al to attempt to define imperialism in terms of statistics, profits, etc. Exploitation is a technical term of Marxian critique of political economy, _not_ an empirically definable quantity. Same with the silly concept of "superprofits." Meaningless.
The political question has always been the same, and it involves _not_ the question of whether capitalism or capitalists _benefit_ from imperialism but the question of whether imperialism is a policy or a mode of existence of capitalism. Arguments over whether an organixm benefits or not from its metabolism would be rather silly. Equally silly is the argument over whether this or that capitalist nation benefits from imperialism.
Carrol