Yeah, the 830.2 is an earlier version of the 836.2.
I am not absolutely positive, but I believe the differences between these two speakers are cosmetic - All screws are hidden behind trim rings and the woofer is anodized to a Titanium color. There is also a 836 which came between these two. I forget the specifics, but it had some, but not all, of the cosmetic changes on the way from the 830.2 to the 836.2!
The 826.2 has a 6" woofer while the other two have a 7" woofer..