Brad,
I have also come across all of the setts you have mentioned, but the Grant, Hunting Grant, Grant of Ballindalloch, and Grant fo Monymusk are the only "official" Grant tartans. The Piper and Champion tartans are derived from paintings of the Grant Piper and Grant Champion. I think it would definitely be cool to get a kilt in either one of those.
When I was referring to the smaller sett I meant that some weavers use a different thread count, but maintain the same ratio thereby keeping the same tartan, but the sett just being smaller. I have a picture on my computer at home with myself and fellow Grant standing side by side. I'm wearing the my Modern Grant in the big sett and he's wearing the Ancient Grant in a smaller sett. I'll try to remember to post it when I get home.

-Will