If you're overdriving your amplifier, or even pushing it close consistently then an external amp should be your priority so you don't burn out your receiver. If you don't expect it to happen again anytime soon, then the second subwoofer should be number 1 (or if the amplifier is 1 then the sub should be 2). You'll gain a lot by adding a second sub, both in output, less power to hit the same levels and smoother overall response. The Oppo really isn't a priority for BD playback. For stereo playback, music files, SACD's, then I'd still put it 3, but then it at least carries a bit more importance. If BD playback is all you're after then you can easily get away with a "lesser" player and be fine.
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