The silence on this one seems odd, given the notoriety of the 923 set. A little digging will reveal the 'crease' issue with this
series and Sony's response to it.
Likewise the GT/VT 30 has it's own share of foibles ; buzzing, fluctuating brightness, green blobs....
Such is the TV state of the art in 2011 . The wisest thing would be to inspect either or both sets in the shop whilst extracting a promise to return if found unacceptable.
Or if you value the opinions of pro calibrators , a well known American guy ( Chad B ) compared the Vt30 with the HX923 for an AV site : makes interesting reading. Let me know if you can't find it.
I think the most important choice for you is that of the dealer to purchase from, given the history of these sets.