SLI/Crossfire, worth it

Is having SLI/Crossfire worth it compared to having one card.

Planning for the future but plan to just use 1080p for a while. 

Whether it's "worth it" depends on the games you play and whether you're willing to put up with odd quirks, and acknowledge that you would have an unconventional GPU setup that is not easy (or possible) for smaller developers to work with. It depends so much on the games you play, that I always recommend people get as much single GPU as they can reasonably afford.

Okay thanks, 

I was considering either a R9 290x or a 780ti

If you're deciding between those, I would say the only factor is cost. 780ti is a couple percent faster (at 1080p), and the 290X is a good bit cheaper.

Cost really isnt my worry i mean i have a budget but its $2000+. I wont be building my computer til the spring. So if i were to go with a card today it would be one of those two, but depending on what comes out in the future will determine what i get. Im also open to any suggestions

in a word, yes 

as long as you have the CPU to drive them and want maxed settings

Get an R9 280 and it will run most games on max at 1080p as long as there are no bottlenecks at CPU or the like.

best bang for the buck.