The 8700/9700 is a good upgrade, but not a giant leap over the 6500ub other than contrast (the 8700/9700 is better in bright scenes and dark scenes actually). Some 8700/9700's are sharper than most 6500ub's, but that really depends on luck of the draw. I owned the 8500ub briefly, and have experience with the 8700ub as well, and the Epson 5010. The 5010 is the best of the 3 because it has convergence adjustment and a brighter best mode, and it's slightly easier to calibrate more accurately, though you still have to watch the sat tracking. I own a JVC RS-45 and Benq w7000 right now.
If you are just looking for the best 2d image for movies and not worried about lag in FPS type games, then you're not going to do that much better than a B-Stock JVC at that price (or B-Stock Sony if you want low gaming lag). The hd8600's IRIS might not bother you, it's hard to say, but Seegs is right, it's not going to be a Sony or Runco quality IRIS where it actually is on target most of the time. I've seen some BAD IRIS's in my day, mainly they just get a bit distracting, sometimes they are bad enough where they don't help much, but usually they still work just with visible distractions.
If it were me, I would go B-Stock JVC over an Epson every day of the week and on Sundays. The Epson is pretty cool, but it's not going to produce as clean looking and as film-like of an image as the Sony or JVC which have a much higher pixel fill. The Epson actually does POP more sometimes if you're into that sort of thing, but the POP comes with a price of inconsistency and sometimes it will suddenly look flatter than the other techs. It's hard to explain, POPs more one moment, flat the next, whereas the JVC is always consistent most of the time (on a good clean source anyways). DLP does POP SLIGHTLY more consistently in bright scenes over both other techs, but it's not a huge difference these days if you calibrate the JVC correctly. The JVC will occasionally look flatter than a DLP. but it all depends on the source most of the time.
Let me summarize by saying this, if you are not going to spend time calibrating, I probably wouldn't even go with the JVC either, get the Sony instead, it looks better OOTB without calibration (in bright scenes at least). The JVC is a tricky beast to get the full potential out of, and it's not just because of color either (which is its own issue), but it's just a multitude of things.
JVC or Sony over Epson though, IMHO...