I purchased Ascents when they went on sale after being discontinued. The pair that I received were damaged at the bottom of the stator in a way that did not affect the sound. Nevertheless, I groused about the damage, and my dealer traded them for Ascent-is (since they could not get any more Ascents). I ended up having the Ascents at home in my system for about 2 weeks, after which the Ascent-is were installed. My opinions are therefore based on speakers that had not been broken in altogether. Bearing this experience in mind, here is what I found:
Stators: There is minimal sonic difference between the old-style panel and the clear-spar. If there is a difference, it did not contribute meaningfully to my enjoyment of the sound or the music on my system (Linn LP12 and Meridian 508.24 sources, Copland 301MKII pre, BC28 amp, VdH cabling). The clear-spars do look a bit neater, and the difference in construction may lead to longevity differences.
Woofers: The Ascents have paper cones versus aluminum for the Ascent-i. I did notice a difference in the bass. On rock/popular music, the aluminum drivers had distinctly more punch and sounded deeper and tighter. However, on classical music, I would say that the paper drivers (maybe) had a bit more body when listening to things like solo 'cello. That being said, these differences did not cause the characteristic sound of the speakers to change significantly. By that I mean that if I heard the Ascents followed by the Ascent-i blind, I would probably conclude that they were the same kind of speakers. So if there is something abou the Ascents that you don't like, I suspect the upgrade will not resolve the problem. If you do like the sound of your Ascents, then spend the money on a weaker component.
All-in-all, I think that the $800 or whatever it would cost to upgrade the panels and woofers (and LED) would be much better spent elsewhere in your system, or as a downpayment into a savings plan for Summits(!). I really love my Ascent-is, but if I had the Ascents I would not bother with the upgrade.