The 450 price comes with 1 "dry" mouthpiece...meaning it is not a water tool, just a dry mouthpiece for inhaling the vapors. It will be tasty with that, but it does not diffuse the vapor and you may still cough with it.
If you want to get a water tool for it, I would go one of two ways. Either buy a nice glass piece on your own from another site, which would allow you to also combust now and then (if you want to)...
...or purchase one of their Hydra tubes to use specifically with the Evo. Like I said, I have both and enjoy using each depending on my mood and how much diffusion I am looking for.
My recommendation at this time is to get a HT. And if you want to save a LOT of money at the moment your timing is great. The HT called the SSFG Hydraline is actually for sale on MassDrop right now and has already reached the lowest price of only 169. Since the normal price is 275, that is a great savings right now. If I wasn't broke right now, I would have definitely picked one up.
Once you start collecting glass you're in trouble of contracting GAS (Glass Acquisition Syndrome). I had it for awhile, but finances have curtailed it for now...but I know it will come back, and I welcome it when it does. A fun hobby and it is great to see how different pieces work.
So, if you're going to purchase today, my "suggestion" is buy the base Evo with the glass mouthpiece and then go over to MD and grab the SSFG Hydraline for use as your water tool. That to me would be a great combo and you should enjoy it very much...