I can't really (mostly due to time available) help you with most of your questions right now, but I wanted to say welcome! We're generally a pretty friendly bunch around here, and thanks for taking the time to introduce yourself.
- I'd like to use JRiver MC as my primary interface to access an NAS device
MC really excels at this. The Media Network features can allow you to stream your media to mobile devices and to other PCs over both your internal network and to the WAN (over the Internet). This works spectacularly well with JRemote on iOS, and with copies of MC itself running on a laptop. I'm not experienced with Gizmo, so you'll need someone else to comment there (and I know this is under active development behind the scenes right now), but it certainly does work.
You can even use the stripped down WebGizmo interface to access your media from any computer or device that has a competent web browser (which is handy if you're at a friends house and just really need to play that one track for some reason).
For media management, I don't think MC can be beat by basically anything out there,
including multiple-hundreds-of-thousands-of-dollar "enterprise" digital asset management systems. Some tips to start from the wiki:
*
http://wiki.jriver.com/index.php/Library*
http://wiki.jriver.com/index.php/Media_Views*
http://wiki.jriver.com/index.php/Media_Network*
http://wiki.jriver.com/index.php/Import - One thing I don't quite yet understand (please forgive my ignorance - been quite awhile since I've set up any system, audio or video) is how I'll be able to interface via my television, if at all. I'm assuming (always dangerous), I'll have to have some kind of computer attached to the screen in order to use any remote that isn't an Android (or Apple, if I ever go back) interface. Is that right? ATM, I do not plan to buy another PC, so I'll have to either find a workaround, or just use my phone, I think. I'd much like to have the theater view on my television, but also understand that it won't magically appear.
Certainly, the best possible scenario is to have a HTPC in your living room, or to run a HDMI from your main computer to the TV (and use a secondary display output from your video card). Those are really the only ways to get Theater View
itself on your TV. I can say that this works pretty spectacularly if you do it.
If you're interested in the latter, yell and I can make some recommendations (or point to previous posts of my own).
If you're interested in the former, then there are a few ways to handle this. One low cost option might be to go with something like the
Intel Compute Stick when it ships in a month or two. JRiver also offers the full-supported
JRiver Id, which is essentially a MC-computer-in-a-box. The IDs JRiver ships, however, are Linux based and the Linux version of MC does not support Theater View at this time. This may come in the future, but if so, it would likely be a "paid" update to MC (such as MC21 or something). To get Theater View now, you have to be running under Windows. Of course, since JRiver allows you to use a single Windows license on multiple PCs that you personally own, you wouldn't need to buy another copy of MC to get this (just a Windows license), and you could even use one of the JRiver-shipped hardware devices if you want, or buy your own).
MC does have quite a few other options, though. It does, as I think you know, have DLNA support in a variety of different ways, which can allow you to push your media across the network to a variety of DLNA devices. Since I'm a HTPC user and there are others here with more smarts in the DLNA-realm, I'll leave those questions to others.
There's also chromecast support and other cool stuff. I sometimes use JRemote mirrored to my AppleTV (when away from the HTPC) and this works splendidly.