Use GPU for floating point calcs

I hope not. GPUs was never thought to do precise reliable calculations. I know that many people try to use them that way, "most smart" from them have noticed that specialized GPU chip based boards for calculations are at least real work capable solution. But that removes the "deal breaker" for original GPU based calculation idea: low price...
 
Modern CPUs are more than capable in audio stream processing. The most problematic point is not the speed but the latency and overall system data throughput (for sample based synths). GPUs are optimized for enormous processing of relatively small set of data with "big" data preloaded: 3D model itself is quite small, but putting  everything "in position", apply textures and smooth the result is challenging task, note that close to nothing "comes back" to computer during this process and small "mistakes" are impossible to notice when everything changes 100 times per second on your monitor. So the latency and the accuracy have no priority for GPU constructors. Music production has different goal, you are using "CPU heavy" FXes and VSTi with GBs of samples and slow conversion algorithm just to get that subtle accuracy improvement.