Speaker arrangement terminology

Hmmm. yeah, I would agree with your description of 6.0 and 6.1.

That being said, in your system, I think I would replace the two HGS-15 with your two HGS-10.  Then connect the big HGS-15's to your Bryston .1 subwoofer output.

The reasoning here is that 2-channel music doesn't necessarily need those extra big HGS-15 (unless you listen to stuff like scrillex and NWA, lol).  However, the HGS-15 would really shine on that Bryston's subwoofer output where you get a LOT of low bass on movie's LFE channel.

If you have two subwoofers, but use a Y-splitter cable on one output of your receiver/processor or if you daisy chain one sub to the other, then it is still considered 1 LFE channel since you are only using one output on your receiver/processor.  So, it would be 6.1 if you were using 6 floor channels.

It would only be considered 6.2 if you used two separate outputs on your receiver/processor to drive two separate subwoofers as two individual discrete analog channels.  In this case, the receiver/processor may send certain sounds only to one of the subwoofers, such as bass from the left main speaker/channel if you have that speaker set as "SMALL".  Any LFE effects from the movie (such as earthquakes, explosions) would be sent to both subwoofers.