Rhapsody's Performance Config is a project intended to supercede Chris' dx9frames config, and be superior in every way. Since Chris' configs were abandoned, this one is the better choice, being that it's active and is updated with more convars that increase performance. Alongside that, it's documented much more thoroughly than Chris' was, and is avaliable in the file for anyone interested.
This config uses Chris' dx9frames as a base, but is completely re-organized in a neater fashion, and is much more user-friendy and intuitive. Everything but the core changes are mentioned and configurable in an in-game wizard, allowing you to choose things as you want them. These changes are saved between sessions thanks to the magic of host_writeconfig, as well, so you'd only need to actually edit the config if you're an advanced user and want even more control.
In order to use this config, you first have to download it. You can do this by pressing one of the two buttons above; either Raw Text or ZIP. If you download it as a ZIP, then all you have to do is extract the archive and find autoexec.cfg. Once you do, just go to the following filepath, and place it there.
C:\Program Files (x86)\Steam\SteamApps\common\Team Fortress 2\tf\cfg
or if that doesn't work, go to
C:\Program Files\Steam\SteamApps\common\Team Fortress 2\tf\cfg
Users/UserName/Library/Application Support/Steam/SteamApps/common/Team Fortress 2/tf/cfg
~/.steam/SteamApps/common/Team Fortress 2/tf/cfg
After you do that, just start up your game and type 'setup' in console, and you'll be good to go.
If you chose Raw Text, then just go to the filepath stated above, copy the text from the browser window, and paste it into your autoexec.cfg file. If you don't have an autoexec.cfg file, then create it.