Since disc space is rarely an issue for me on Blu-ray projects, I render audio as PCM at 96kHz / 24 bit to drop into DVD Architect. My sampling frequency and bit rate makes sense, as it does for me, only if source audio is at least this good -- I actually downsample from my audio recorder to 192 kHz / 32-bit floating. So rendering for DVDA constitutes a further downsampling for me.

HTH,
Steve