Many places that sell high-end TVs, including Best Buy's Magnolia guys, will haggle.
Best Buy officially won't price-match, but in practice, they usually will. Bring a print-out of an online price and they'll most likely match it.
My TV had a sticker price of $2499 at Best Buy and they price-matched it at $2099, then accidentally opened the box moving it out of the shipping room and unexpectedly sold it to me as an open-box item for $1899 with some minor free throw-in like a Monster surge suppressor (don't remember now what the throw-in was). It helps that it was an older (but still great) model that was about to be replaced. In my case, it's the 46" Sony Bravia with local LED backlighting - one of the best pictures I've seen and generally great in every way except not super-thin (regular flat-panel dimensions) and no Internet widgets (which I get from my FIOS service and Apple TV anyway so I don't care).
For the original poster, how big is the TV? Amazon has the 46" version right now for under $2800.