You can use FRAPS with a dual-GPU setup no problem. You can get good deals on the R9 290x right now. If your plan is to either get two R9 290xs or one GTX 980, you're going to definitely get better performance out of 2 R9 290xs. If you run at 1080p or 1440p resolutions, even a single GTX 980 is great and you can always get another in a couple of years if you feel so inclined. You'll pay a bit more for the two 290xs, so it just comes down to how much you want to spend. Both are good solutions. The 2 290xs will give substantially better performance over a single GTX 980 if the drivers for crossfire are reliable.
When it comes to SLI, I haven't run into a single AAA title that wasn't SLI-ready within a couple of weeks of release at most. SLI tech never gave me any problems. I had an SLI setup with 580s, 680s, and 780s. Drivers for crossfire with Radeon 5850s on the other hand was bad for me and is what made me switch from being a long-time ATI/AMD customer to an Nvidia customer. I've heard crossfire has gotten better after the whole FCAT scandal, but I'm still a little gun shy when it comes to buying any AMD video card. As a result, I'd recommend the GTX 980.