That's a really nice TV. Personally, I think if you don't get some type of HD player then you wasted $2,000. You can try a test if you like. Switch your XBox 360's output to 480p and play your favorite game. Then switch it back to 1080i and see if you notice the difference. It should be pretty drastic.
Also, keep in mind that visual quality is not the only advantage HD-DVD has over standard def DVD. You also get more special features on your discs. I'm a huge Superman nerd and when I bought the Superman Returns HD-DVD I was shocked at how much extra footage was on the disc. You just can't get that from DVDs.
Think of it this way: You bought a $2,000 TV and a game console that cost $300 - $400. Let's say you spent $2,500 when all is said and done. For less than 8% more you can enter the world of HD players. The choice is yours. It just seems like a waste to me if you don't use such a great TV to its fullest potential.