If you plan on buying them eventually then I would take advantage of the discount regardless of when I was planning on installing. If you wait then it may take time to find another 10 ppl for a group buy to get the discount at that point in time(My opinion)
Sounds like it, which means you have to find someone to inspect it that is not reputable and hope you never get checked by DOT.
Not sure about where you live but finding a garage to sticker an illegal set-up is getting harder and harder around here.
I was going to do it with my diesel but after checking around no one would put a sticker on it.
Oh and it does sound nice though! But!
Unless they changed things, I put a single stage flowmaster on my 97 Toyota T-100 and it sounded even better then this does, that is just a muffler swap.