I think your bow is probably fine for you.

I have an 05 Defender and it's a really nice bow. I shot the 06 Tribute and I think it is just a little bit better than mine. I want it, but it's not worth the $$$ hit I will take to upgrade.

Bows are like computers now. Every year they have new inovations and get better. More speed, more forgiving, less hand shock, quieter, etc... The problem is, unless you are wealthy, you can never be cutting edge two years in a row. If your bow is still taking deer, then it works. You will have to decide if you can afford it. Looking at the prices that you posted, the guy isn't giving you any breaks.