So I contacted sonylistens, and got a "Event ID" number and a phone number to call. When I called (it took three different attempts to get through to someone who sounded like they were in an overseas call center), I was offered the following choices (and seven days in which to decide):
KDL46EX500 - $415 + tax
KDL55BX520 - $575 + tax
Part of me wonders if the color uniformity would be better with a EX500 or BX520 CCFL LCD rather than an edge-lit LED (everyone seems to want "thinner" sets but it's not clear to me that LED makes for a better image). That said, the 55BX520 won't fit in my entertainment center since at 52 5/8", it is too wide. I'm sending a follow-up email to sonylistens to see if I can get an offer on a 55EX720 or 55NX720 instead, though I'm not thrilled about having to spend over a thousand bucks on a replacement set at this point.
I've heard others suggest maybe getting a smaller set (like the 46" or maybe even a 40") and using it in another room and instead looking for a better replacement for the SXRD, like maybe a Panny Plasma, though their 55" models are also just a smidge too wide which makes me want to wait and see if 2012 brings models with thinner bezels and thus narrower overall dimensions. I might also look into getting the optical block repaired as others have done to see if that buys me a little more time...
Anyway, thoughts on PQ differences between the EX500, EX720, and NX720 would be appreciated. I've found helpful comparison charts (on various Amazon product pages) showing the technical differences (CCFL vs edge-lit LED vs dynamic edge-lit LED, respectively)... Just trying to decide whether to "go cheap" for another room or whether I'd be happy with an EX720 (if I can even get them to offer me one)... Any comments or suggestions?