The answer is dependent on the quality of the crossover in the subwoofer but I suspect that, in the case of using a 1/8" ouput from a typical PC, it will not be significant.
If you were using an external, high-quality DAC, I would have greater concern. In that case, the better but costlier route would be an external crossover.
If you were using an external, high-quality DAC, I would have greater concern. In that case, the better but costlier route would be an external crossover.