I'm just going to go ahead and order the MSI R9 270 for $190. Seems like it's a good price for what it can do.
I have 50+ users using OpenCL every working day using Radeons. They're the best option for the majority of OpenCL applications, and that includes 3D rendering and compute tasks in general. I tested our four main applications with Radeons, Geforces, FirePros and Quadros (because they were on-hand). Radeons are at the top of the price/performance curve by some margin for us, that's for sure.
Occasionally you'll wish you had an nVidia card because biased/backhanded vendor X
has chosen or been finacially incentivized to optimise solely for the proprietary
nVidia CUDA API. Proprietary never ends well, it is a dirty, selfish, industry-crippling word;
OpenCL applications already outnumber and outperform CUDA alernatives for the most part, because developers have started to realise that AMD's GCN cards are an OpenGL compute monsters in comparison to Nvidia's shader-optimised gaming cards, complete with the full-market benefit of open-standard goodness against the nVidia-controlled captive audience of CUDA.
Am I biased? Maybe, though I'm not trying to unfairly represent CUDA, because it's very capable as an API.
Am I sick of nVidia's marketing bull****, selfishness towards industry standards, and ridiculous Quadro pricing? Hell yes.