The X-LS, and presumably the X-SLS can take plenty of power. Do they sound good? You've already read reviews. They have some minor issues, but they also have some upgrades available as well as new versions of the speakers coming out very soon with many of those upgrades for not much more. They can handle metal, but may not suit your needs 100% if that is all you are going to play on them. I would recommend trying the 30 day risk free trial of the X-LS and know for sure if they are what you need.
If it is metal you are after though, you may want to go with Klipsch...
These two brands could not sound more different IMO, so you aren't comparing apples to oranges.
What do you plan on powering them with?