spgator, I am running the 600000 in my car now. IMO, it is one of the best small format tweeter money can buy.
But there are a few people running the 700000 here. I would say the 600000 is no match with the 700000, in all aspect (details, airyness, refineness, extensions etc). Every time I sat in their cars, I notice the difference. It is not that 600000 is not good. Its just that the 700000 is too good....
Anyhow, try it out first and see whether you are happy with 600000. Everybody has its own taste.
Welcome to the scanspeak club !