So right now I have an 02 400ex with a stock motor and a slip on exhaust. I went 1 tooth down in the front and 1 tooth up in the back. I'm a little guy I weigh 120 pounds so me on my 400 will go up anything at Winchester bay sand dunes, I can make it up banshee hill in 3rd and the lake tree shot anytime of year. I really like my 400, I love its reliability and how I can change the oil every few dune trips and I love how I can let the clutch out and give it no gas and it just goes. But it just doesnt go up hills at the dunes as fast as i would like. So I've been looking into buying an 04 or 05 trx450, but I know that they are a lot more to take care of and not as reliable and I LOVE the low end torque of my 400, so do you think I will miss my 400, or not? Do you think I should save up some more and keep the 400 and have both? What are your thoughts?