Sorry for the naive question - could you please explain the difference between the way that the G98DH sends DVDA as compared to the OPPO. I understand that the G98 can grab the native 96/24 off the DVDA tracks and transmit that over the proprietary MHR to the G68. Will the OPPO also send 96/24 to the G68? How about the new TrueHD and DTS MA (?) formats - will these be decoded by the OPPO or by the G68?
The Oppo will decode DVDA, TruHD and DTS-MA to PCM and send that to the G68. Of those formats the G98 can only play DVDA, but can as you write use the Meridian-proprietary MHR which is said to give lower jitter than most other product combinations. But if/how much you will notice jitter we can't say. The CHT clock-upgrade is a possible way to reduce source jitter in the Oppo. The G98 will be better, but the Oppo will possibly be "Good enough" - you can't here the difference (?)
Regarding the status on playing stuff from an external USB drive I neither know what Oppo has planned nor what the current FW can handle, there's too much line noise in the AVS forum. But I've read about the limitation of FAT32 disks only, no NTFS.