If you are a stickler for legal purism or cannot tolerate emulation glitches, wait for an official re-release (which will likely never happen due to music licensing and wrestler contracts).
WWE SmackDown vs Raw 2006 Definitive Edition Repack is available to buy on a range of platforms, including Steam, GOG, and the WWE Shop. Be sure to check out the game's official website for more information on where to buy and how to download. wwe smackdown vs raw 2006 definitive edition repack