The speakers on the HX929 suck too. Don't go looking for a TV with "good" built-in sound, because you won't find any any more.
Since your TV is more than a few years old, there's not going to be anything completely equivalent to what you had...notice how they replacement they offered you is actually 3 inches bigger than what you had, since sony no longer manufactures 52" sets. Analog inputs are almost non-extant on today's sets. While I don't really remember the picture quality of your XBR6, I would agree with Steve here in that it would probably be esily exceeded by a 2011 mid-range panel like the NX720. "XBR" designation or original MSRP are not really what you call specifications on which sony has to match.
ht Panasonic TC-P60ZT60, Monitor Audio: Silver RX6, RX Centre, Radius 90HD; Martinlogan Dynamo 700, Marantz SR5006, PS3, Oppo BDP-103D
2ch Marantz PM8004, Sony BDP-S1000ES, JVC T-X3 tuner, Monitor Audio Silver RX1, REL T3, Apple TV, Peachtree Audio DAC•iT
lr Panasonic 50ST60, Sony BDP-S5100