with contacts: Kenko DG Auto set. 12+20+36
They're about $200 at Adorama or B&H. Not cheap, but I use them a lot, so I think they're worth it.
If i recollect correctly, 68mm of tubes puts you at 3:1, close enough for me
Not to mention being able to retain aperture and AF is a huge plus in my book and worth the price considering i'm nowhere near steady enough to use the MPE-65.