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The 490K MPH is of course relative to the center, so it's not really a meaningful comparison. Obviously there's a broad range of relative velocities between the stars, and this Orionid junk has some kind of relative velocity. I'm not suggesting that the Moon came from there, only that large impactors / interlopers could indeed come from outside our system.

The Cycle of Cosmic Catastrophes:
Flood, Fire, and Famine
in the History of Civilization
by Richard Firestone,
Allen West, and
Simon Warwick-Smith

Re: the 490K MPH

That velocity is of course relative. It would probably be more accurate to state that it is relatve to some fixed coordinate in the universe around us than the center. It is however the shared velocity of everything in this particular orbital distance from the center.

A hypothetical body wandering in from interstellar space would most likely be moving far slower especially to be slow enough to either be captured in solar orbit or to not impart a solar escape velocity to an impacted early Earth. (This raises the question of why such a high velocity collision did not impart a highly elliptical orbit after combining their inertia.) The length of time necessary to reach Earth over stellar distances is further increased... by a lot. This decreases the candidates for its source even more. This wandering rock would have to come from somewhere close to be at the required velocity to meet the criteria for our Moon maker.