I don't think the sample rate is the issue.

Is there a place to adjust the number of samples being buffered by your SonicCell? This can be done sometimes in the music application, like Logic. Sometimes there is an applet for the sound card. The applet might be a stand alone app or could be in Control Panel. If you can find it, make the number of samples larger. Say from 256 to 512. This will probably fix the stuttering problem, but raising the number of samples processed will introduce a small amount of latency.

Some sound card managers let you adjust the buffer time, instead of the numbers of samples. In that case just increase the number. Say from 1ms to 2ms.