Older GPUs and AMD APUs certainly seem to be more productive with the stream app. I stumbled into a solution for this on one of my rigs, but I am not sure if I could do it again. I installed an AMD card, then ran Driver Sweeper on the old Nvidia drivers, which removed the openCL driver. Now Moo runs the ATI app, but if I want to run any other GPU projects I'll have to reinstall the AMD drivers to restore openCL.

Your 270x should run fine under the new app, though. Have you tried it?