Zach,welcome. That's an excellent price for the 635 and it's hard to imagine how you'd do better. I'd suggest that you forget the "no matter what" part however, since it's entirely possible that the 635 will have more than enough power for your M80s in your listening room.. There's a tendency to overestimate power requirements and to spend money which could be used better elsewhere on power which will be unused.

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Enjoy the music, not the equipment.