Possible (and yet-to-be-proven) collectability aside, I can't see spending nearly TWICE the $ for an ersatz M1.
True, Springfield Armory Inc. has a good rep. And the cast vs. forged receiver debate is moot, I think. Never heard of an M1A receiver failing due to its being cast, so the at least as strong, if not stronger M1 receiver should be able to take it.
A DCM M1 IS collectable, and WILL appreciate. If there's a legit problem with it (possible, but unlikely) DCM has a reputation of bending over backwards to satisfy customers.
If you get a real mixmaster, you can restore the rifle to "as-issued" condition at small cost via swapping out parts.
If the barrel wears out too soon for your liking, replace it with the "correct" GI bbl, or screw on a Match-grade 7.62 or .30-'06 tube.
Finally, there's nothing like owning a real piece of history.