Hey Matt, welcome to the forum.
I think that before you think about investing in the Aria electronics package, you should try doing some recording with your Otari in stock form.
One of the reasons that you won't find as many threads regarding upgrades of the record electronics is that in most cases, it's very good. There are ways to maximize the record section of most machines but you are talking about somewhat small improvements compared to what can be done on the playback side of the equation.
I'm not familiar with the Aria electronics and the interface with your machine should be discussed with Mike Spitz, the owner of ATR Services.
Regarding balanced operation,..
When it comes to semi pro and professional audio gear it refers to how the equipment is connected. In a professional setting, the need for long runs of cable are the norm rather than the exception as in home audio. Having 200 feet of cable is needed when you're talking about a live stage show (think about how far away the soundboard is from the microphones and the speakers that it controls). Because of that, a tiny signal
will pick up a lot of unwanted noise. Because of these situations a standard line level of +4dB is used along with a 3 wire cable to assure a grounded shield that's not connected to the signal wires. The 3 wire connector is either an XLR/cannon or a TRS 1/4" jack.
The consumer level is -10dB. I suspect that this is mostly a cost issue. Most pro gear employs a transformer to raise the signal leaving a piece of gear and another transformer to lower this level as it enters the input of the next piece of gear. These transformers could easily be the single most expensive components in the gear . And, no matter how good a transformer is, it's another thing in the signal path so it changes the sound.
There is an excellent paper on balanced cabling here;
http://www.rane.com/note110.htmlThe audiophile use of the term
balanced is more of an internal design idea. The level of the inputs and outputs of this gear varies with the manufacturer.
There are other uses of the term balanced in audio but I think the water is muddy enough as it is.
BTW to learn more about the wonderful world of reel to reel, check out the stickies at the top of the " General Forum". They're packed with info.