If possible at all, see the TVs in a dim surrounding cos the usual showroom floors are way brighter than your usual viewing at home. One place I remember is Harvey Norman at Millenia Walk. They have one wall which is specially dimmed for some of the flat panels. Trust your own eyes.
You may also want to check out Xtremeplace.com for more expert advice. BTW, these TVs are actually still LCD TVs. They have just replaced the CCFL tube backlights with LED backlights. True LED TVs have yet to hit the consumer mass market. Don't get fooled by marketing.
BTW, for over 40 inch sizes, and especially if you go bigger, worth considering the plasma panels too. The bigger the panel, the more costly LCDs get.
het,
I think you made a mistake with your TV specs -- contrast is not measured in mHz. If you committed based on that, then you probably made a mistake in relying on some figure that you didn't understand. But as long as your eyes like what you see, that's what matters.