I may have missed something in this thread, but it appears that the OP was dealing with the manufacturer's distributer of the product, directly as a retail customer. He did not know what interfaces and auxiliary products were needed to make a complete system, custom for his unique airplane.
The person he was talking with was not skilled in such, they were an order taker for avionics shops for wholesale orders, prepared by experts in the avionics manufactured by that company. The order clerk had to find an engineer with time to spare when the order taker also had time to spare, and figure out just what the OP meant by the question.
Then, when the return call about the question was made, the OP did not even remember the exact question asked, and had more questions.
He should be dealing with an avionics shop, with the added price for the time needed by an expert to put together a compatible system for his plane. Experienced employees cost money, and their time must be paid for.
Even if the OP brings in his system in a cardboard box, pre engineered by some anonymous person, the shop will have to do due diligence to assure that it is complete and compatible, as they have the liability if the OP specified parts do not play well together.
The warrantee situation if he had bought the parts, and a problem developed with a defective component, his recourse would have to be through a retail shop, factories do not have that function. The avionics technician who determined the part defective is the one who must convince the factory to make good on the part. He has modest interest in pursuing the issue, as he made no commission on the sale. He will be paid by the OP at his hourly rate for the testing and negotiations with the factory.
There is a good reason most owners go to an avionics shop to buy their new equipment.