There are likely to be arguments on both sides as to which is better, using an analog crossover with only one D to A conversion or using your digital crossover with required sample rate conversion. What I would suggest would be to convert DSD256 to 176.4/24 PCM (assuming that's an available and supported option) instead of 192/24 since the DSD sampling rate is an integer multiple of 176.4 and it's not of 192 so the sampling rate conversion is much simpler.