Yes, keep it going!
Right now I'm still leaning towards installing an Ethernet cable for piece of mind. If I do that, then the question is do I go with CAT5e, CAT6, or CAT6a? If cable length matters, it will be about 70ft.
So many questions!
Edit: I see there is CAT7 cable now. I'm guessing this would really be overkill.
Edit2: And I see there are shielded and up shielded cables......which would I need? I have a headache now.
Don't get too much of a headache over this. It looks like a lot, but it is simpler than it looks.
These are each newer and newer revisions for the computer industry specification for the same kind of basic network cable. First, you are fine at 70ft; these cables can be up to 100m in a single run (say from whatever magic box gets your Internet into the house to the streamer in this example). Just be mindful of the path you're pulling the wire through to make sure it doesn't get kinked, twisted, or bent at an extreme angle somewhere along the run so that the wires inside the cable don't get pinched, stretched, or stressed.
Next, any of them will work for this application, the difference is in the maximum speed the wire can send data, but that might be limited by what devices the cable is connecting together anyway if you have some older computer network equipment. Note that the Salk Streamer can send data up to 1Gbps, and a lot of off the shelf home network equipment is running that speed these days, so if you aren't already at that speed in the house you likely will be shortly due to normal hardware upgrades.
[NOTE: Please, for sake of this specific post, let's avoid the usual audiophile discussions about cables and assume wire is wire and bits are bits. This post is just meant to explain what to get to make it all work. - Thanks!]
To use something you're probably more familiar with, the difference is similar to the way USB 1.1 - USB2 - USB3 work. All of the different USB cables are backward compatible, interchangeable to a point, and the later versions can run faster than the earlier ones limited by the slowest link in the chain.
All these network cables are the same way, in order of: Cat5 - Cat5e - Cat6 - Cat6a - Cat7, each varying in maximum speed data can move:
Cat5 can run at 100Mbps
Cat5e can run at 100Mbps and up to 1Gbps with some limitations
Cat6 can run at 1Gbps
Cat6a can run at 1Gbps, and up to 10Gbps with some limitations
Cat7 can run at 10Gbps
[Just an FYI, but there is currently a Cat7a specification, and the Cat8 specification is in the works, moving up to 40Gbps speeds.]
What you end up putting in is really a function of how much money you want to spend on the project and how far "future proof" you want to make it (by this it is assumed you are going to want to run even faster network speeds than you might have going now). I won't speculate on costs or pricing on cable, but just remember any of them will work, and because the Salk Streamer can run 1Gbps on its built-in network card, I probably wouldn't put less than Cat6 cabling in if I were putting it in new today unless I was really desperate in scraping by on the lowest budget possible.
EDIT - I forgot your question about shielding. All of them are shielded in some way per their specifications, and usually the bulk cable meant for in wall runs has additional shielding for various reasons (usually starting with reducing issues brought up earlier with RF interference from close proximity electrical power wires). For this specific purpose, more is probably better, but remember the cable will be be more physically stiff with the additional shielding.