Sli or Crossfire Ready

Solution
From Corsiar's own product page: http://www.corsair.com/pt-br/cs-series-modular-cs550m-550-watt-80-plus-gold-certified-psu

"CS Series Modular power supplies are ideal for basic desktop systems where low energy use, low noise, and simple installation are essential. 80 PLUS Gold efficiency reduces operating cost and excess heat. Flat, sleeved black modular cables with clearly-marked connectors make installation fast and straightforward, with good-looking results."

SLI or Crossfire would not be considered a Basic Desktop - so No.

If you post what GFX you wish to SLI or Crossfire, we could recommend a PSU for the job or determine if this is adequate.
From Corsiar's own product page: http://www.corsair.com/pt-br/cs-series-modular-cs550m-550-watt-80-plus-gold-certified-psu

"CS Series Modular power supplies are ideal for basic desktop systems where low energy use, low noise, and simple installation are essential. 80 PLUS Gold efficiency reduces operating cost and excess heat. Flat, sleeved black modular cables with clearly-marked connectors make installation fast and straightforward, with good-looking results."

SLI or Crossfire would not be considered a Basic Desktop - so No.

If you post what GFX you wish to SLI or Crossfire, we could recommend a PSU for the job or determine if this is adequate.
 
Solution
A PSU has no idea how many graphics cards you're running nor does it care if you run them in individual or SLI or CF mode. Everything attached to the PSU is seen as an electrical load with no distinction as to the device type it's powering.

Without providing the specific graphics cards you're planning on using it's just a guessing game.