Hi ramses,
Thank you so much for your thorough and greatest advice, and many apologies for a late reply. I took some time to read up on the matters mentioned by you.
About the 3 “Cases” that I’ve mentioned in my last post, you are absolutely right about all 3 cases. The Case 1, where I purchase Pro Tools HD/HDX, is out of question. Like you correctly pointed out, it is a waste of money, and I’ll be “locked in” with Pro Tools for many decades. On top of that, as Pro Tools related hardware depreciate at the speed of bullet, it makes not sense to incorporate Pro Tools into my system at this stage. The Case 3, where I connect ADA-8XR directly to PC is ambiguous, as there is no specific and apparent solution in place. The Case 2, where I connect ADA-8XR to UFX+, undoubtedly, is the best way forward.
Your recommendation to use MADI/AES converter is fantastic. You have kindly recommended two RME converters (RME ADI-642 and RME ADI-6432),and I believe these two are the best MADI/AES converters for my set up.
Given your great advise, I proceeded to search for used piece of ADI-642 and ADI-6432, and I found a few of them. I then made a a purchase of ADI-6432 R BNC (not ADI-6432), which was my mistake. Yes, it is almost like a joke.
Being a beginner, I did not know the differences between AES (110-Ohm, XLR or D-Sub cables are used) and AES-3id (75-Ohm, BNC connection). To quote some of the descriptions on AES and BNC:
“AES3 (hereby referred to as AES for simplicity) specifies balanced 110-ohm interconnects; however, AES-3id calls for unbalanced 75-ohm connections, which make its hardware requirements the same as S/PDIF connections, though usually AES3id is implemented with BNC connections instead of RCA-type connections. While the two formats (AES & AES3id) have different hardware transmission methods, the data contained within the transmission is identical.”
At the back panel of ADA-8XR , there is a D-Sub (25 pin) I/O connection points. This is to be connected to a squid cable (provided by Prism Sound, XLR cables with 110 Ohm). On the back panel of ADI-6432 R BNC, there are unbalanced 75ohm I/O connection points. So in connecting ADA-8XR and ADI-6432 R BNC, some new question arise:
Q1) Would it be possible to connect the ADA-8XR and ADI-6432 R BNC, through the squid cable (XLR, 110-Ohm) attached to ADA-8XR, with BNC I/O (75-Ohm) connection points of ADI-6432 R BNC?
I presume the answer is “Yes”, if there is a good digital audio impedance transformer (which is also known as Balun) for interfacing the XLR cable (110-Ohm) and BNC connection points (75-Ohm) of ADI-6432 R BNC. For example:
XLR(Male) - BNC (Female)
https://www.bhphotovideo.com/c/product/ … 3EQAvD_BwE
XLR(Female) - BNC(Female)
Q2) Say, the issue under Q1 is fine & sorted. Then the next question is how to ensure these impedance transformer (Balun) can efficiently transfer signals without any losses, noises, etc? And any band width issues to deal wtih? Some impedance transformers like that one below is able to accommodate up to 6M Hz, it states. Would that be sufficient for my set up? I have no idea on the sufficiency & benchmark here.
Q3) Would it be easier and convenient if I sell off ADI-6432 R BNC and get ADI-6432? In this way, I do not have to deal with impedance transformer (“Balan”)?
I found some information on the RME forum about the compatibility of BNC and below. Although the case mentioned in the form below is different from my situation, there are some information that are useful.
https://gearspace.com/board/music-compu … ences.html
Some issues of conversion are mentioned on the write-up below:
https://www.tvtechnology.com/opinions/c … aes-inputs
And here is the question that I need to answer for my ongoing action. Should I proceed to sell off this ADI-6432 R BNC and buy ADI-6432? As I purchased ADI-6432 R BNC at a good price, I don’t think I’ll loose any money if I sell this off. I would appreciate if you could point out the right direction for my next move!
On a separate topic, for the last few days, I forwarded my enquiry to Prism Sound about how to incorporate ADA-8XR into my system. In short, they were quick in getting back to me (3 days) but I was mildly disappointed with their very general answer that does allow me to take any actions. 
Well, no manufacturers offer the same level of support as RME, I guess. Here is the answer I’ve got from Prism Sound.
Your ADA-8XR has AES and Pro Tools HD connectivity. So it can probably connect to your computer via the AES i/o on your UFX+. So this is case 2 but it only gives you two channels.
Case 1 works but is expensive and locks you into Pro Tools software I believe.
Case 3 maybe your best option and would involve buying an AES sound card for your PC such as one made by RME perhaps.
Also for case 3, you could buy a firewire card for the ADA-8XR and a PCIe firewire card for your PC assuming that it doesn't already have firewire. However firewire support is becoming increasingly difficult so I don't really recommend this 100%.
On a separate topic,I’ve read your write-up on ADI-2 Pro. You really know your stuff, and you really write so well! Very logical and thorough, as always. And I am now very keen on tyring out M-1610 and ADI-2 Pro! But first thing first, I need to sort out this issue on ADI-6432 R BNC for UFX+ and ADA-8XR!
Thank you for reading my leanthy post ramses. Your valuable input on my next potential actions would be much appreciated!! 