Originally Posted by TIME2PLAYDAGAME
I don't know about what was said above as far as the ST having identical PQ as the GT
I don't know that the PQ of any two sets (even GT vs GT) are technically "identical". But for all practical intents and purposes, most people seem to think that professionally calibrated STs and GTs are close to, if not, indistinguishable. That said, I've seen several people lately picking up GTs for $50-100 more than the their equivalent sized ST counterparts. I'd make that choice in a heartbeat just for little stuff like the dual-processor or in the case you're not getting professional calibration, bigger stuff like THX modes.
So, for me, I definitely wouldn't let a lack of one store's inventory make me step down from 55" to 50". I'd first try to pricematch a GT in the size I wanted to a similar price of the ST and then I'd look elsewhere. Or as highdef mentioned, buy it now and pick it up over the weekend.