the 950s wont cut it. Nvidia's multi-gpu SLI is actually hindering performance.
http://www.tomshardware.co.uk/steamvr-performance-test-gpu-comparison,review-33488.html
"The only real reason we included the 950 was to harness two of them together in SLI. A pair of 950s offers similar gaming performance as a GeForce GTX 970, so we were hoping for more from this configuration. But SLI doesn't work the same in VR and Nvidia hasn't perfected its mechanism for rendering individual screens with separate GPUs yet. As a result, our system's score dropped to 1.2, yielding a "not ready" rating."
"Our R9 390 from Sapphire performs admirably, returning a score of 7.1 at high fidelity. XFX's R9 390X isn't far off, again treating us to high fidelity, this time with a score of 7.6.
Both of those cards outmode Nvidia's entry-level VR-ready GeForce GTX 970. Our Gigabyte GTX 970 WindForce OC manages high fidelity, but achieves a slightly lower score of 6.9."
Do yourself a favor and get an R9 390