I would suggest you just use the 205 as the prepro and use a good pair of XLRs to hookup the stereo l+r/front l+r Oppo outputs direct to your Meridian 568 5ch amp. Then hookup the rears and center direct to the 568 via rca unbalanced cables. The result is simple, direct and streamlined connections between prepro and amp that I'm almost certain would sound very good.
This is the hookup I use on my Oppo 105 and I know for certain that it sounds very good for both 2-ch stereo and 5.1 surround. Including your g68 AVD and HDMI switcher in the chain seems redundant and unnecessary to me. The 205 uses multiple excellent and expensive Saber dacs with volume adjustments communicated digitally to, and actually performed on, each channel's dac chip so there's no dropped bits and missing information.
There's also also an audio setup menu that allows you to set the relative volume of each channel and whether or not you want bass assistance from your sub. But there's no actual room correction with a mic, software and parametric equalization. It's completely sufficient for my needs but may not be for yours.
I'm really not familiar with the performance level of your g68 and whether you consider room correction a requirement but, of course, you could always audition and compare your system performance with and without the g68 and just choose the one you like best.
Tim