try to enhance 3 or 4 of those armonias in a row, i think you'd get atleast one of them to +7 tho(still no guarantee, and failure means you lost your weapons) and yea, it cost much more than buying already made one, except not that many people selling their armonias+7.
i got all of my +7 stuff(33ar one xD) from this new(not so new anymore) enhancement system. cos before, those anti-destroys(if you refering to that system) is frickin expensive, well, you wont lose your weapon, but i hate how many times i need to buy them and then keep trying. personally, i like this one better. like i said long time ago, you need guts to enhance to +7 now(and God-knows-how-much-grinding-to-be-done).