Yes it can. The Obsidian case can handle up to 340mm GPU's (Link here - look under Tech specs tab
GPU is listed at 305 mm HERE
. I'm extracting the 12" length to 304.8 mm, doing the math. Also the price, for the GPU, at Newegg is ~$35 cheaper, depending on your taxes.
Personally I would go with the R9 290 instead of the 290x, if it was up to me. It costs less, consumes less power, & performs quite well for the $.Here's a list of 290's that I'd consider.