The CUDA technology is prioprietary to NVIDIA, so it supported only by NVIDIA graphics card. Shapespark doesn’t support baking on AMD cards.
What CPU do you have? Recent many-core CPUs are also fast in terms of baking.
Furthermore, have you tried baking your scenes using our beta cloud editor: Beta release of the Shapespark cloud editor ? Our cloud machines have 128 cores, so should be significantly faster than the hypothetical baking speed of Radeon 6650 XT.