I have some info for you, but I think someone else may need to chime in here as well. I just got my setup established last night so I'll try to answer your questions and give an update on my experiences so far.
I have TMT5 and it has been great for lossless playback. I am leaning toward picking up jriver so I can get the advanced features like room correction, phone/tablet based interface to manage movie and music playback, and JRiver seems to be good for dealing with blu-ray rips. It does a lot more than that, but those items jumped out at me. JRiver seems like an awesome setup. From what I have gathered JRiver will decode TrueHD and DTS-MA and output via analog without down sampling. This requires the correct .dll's but those are easily obtained. After decoding, protection is completely removed and analog output is just fine to the amp(s).
I ended up getting and setting up the HT Omega Claro Halo XT last night and my initial impressions are excellent. Setup was incredibly easy and the drivers appear to be very stable. I listened to music via Grooveshark, tested a few blu-ray titles in TMT5, watched OTA TV using a Hauppauge WinTV-HVR 1850 in W7MC, and used the Optical S/PDIF Input from my Direc TV box (subscription expiring shortly with no desire to renew) and a friend's PS3. All of these scenarios were outputted via analog to Outlaw 2200 monoblock amps, then to speakers. The results were awesome. The last item involving Optical S/PDIF has one caveat, you can only receive 2 channel PCM via this connection to the Halo (this is a connection limitation). You can, of course, mix that to 5.1 or 7.1. I am using 5.1. The sound is still very good. Considering it isn't an everyday thing for me, I don't mind. If a friend brings their console over, we can still play it with great sound. That's a win for me. My gaming system is the PC and it absolutely KILLS consoles, so I don't mind. PC gaming is 5.1 goodness all the way. Oh, I forgot to mention, I did play some Skyrim last night
I don't know how the Halo compares to the Xonar DX. I used to have the Xonar HDAV1.3 which was a good card for its intended purpose at the time. The Halo does a hell of a lot of things that the Xonar DX wont do though. In addition to feature, what sets HT Omega apart from Asus, is customer support. I have a real world example of this, experienced yesterday, which makes me a huge fan of HT Omega. I'll relay this so that everyone can see how unbelievable (at least to me) their service level is.
12:40 PM PST - Sent email to HT Omega with question regarding listening to the Optical S/PDIF input. The "monitor" setting is way too loud. I had to select to listen to SPDIF In for Recording Devices in Windows Sound setup. It's an easy process but I didn't know how to do it before contacting customer support. So I sent my email and expected a reply in a few days, if at all, like most vendors.
1:39 PM PST - Reply sent by HT Omega support with information and clarifying questions.
3:32 PM PST - I sent my reply. It took me almost two hours because I didn't even notice HT Omega had replied to me. I wasn't expecting their reply for for a while based on my experience with most vendors.
4:24 PM PST - Reply sent by HT Omega with detailed description of S/PDIF capabilities on the Halo and three screenshots with added markups by customer support to show me exactly how to listen to this connection via Windows. It worked flawlessly. I can mix this to 5.1 if I wish and control volume the same as I would with anything else.
Just to break this service level down:
Time for first reply from HT Omega - 59 minutes
Time for second reply from HT Omega - 52 minutes
I seriously couldn't ask for better service. This has made me a TOTALLY satisfied Halo XT owner.