Yes, there are a lot of options out there, so it's a challenge to know what to do.
As for the 5D Mark III, they're marked down to $2699 at Amazon as well (as of this post).
But I agree with Noam. The 5D Magic Lantern hack is too much hassle.
If you decide not to go with the RX10's smaller 1" sensor, I like your idea of getting the full-frame $1998 A7 for stills and the $995 BMPCC for video.
For about the same price as the 5D Mark III, you'll have both a high quality full frame still camera and a purpose-built ProRes + RAW cinema camera that is being used to produce some awesome professional work:
Chrissy DePauw Electronic Press Kit by Kofa (ProRes):
Barts Clothing Commercial by Whitemotion Pictures (RAW)
"The Case" – real estate video from Paper Crane (ProRes)
Hope this doesn't mess your plans up again! Hope you're having a great holiday season,
Bill
Hybrid Camera Revolution
