Hiya Houghy,
You are able to use the DSI & LPI to guide your LX200 from within Autostar Envisage. Just type COMx into the port box and hit CONNECT (x = 1,2,3,4 or whatever your serial port number is).
Unfortunately K3 & Guidedog do not support the DSI, but I think the LPI should work ok here.
To autoguide your EQ6 Skyscan you'll need an interface between the mount and the PC. If you are using K3 and/or guidedog (LPI only) there are a few options for this interface including my LX200 emulator box.
If you want to use the DSI to autoguide the EQ6 (dimmer stars than LPI) then you are limited to the Meade Envisage software. As far as I'm aware the only way to communicate with non-Meade mounts from within Envisage is to use an LX200 emulator box. As far as I know my star-mate LX200 emulator is the only one that works "properly" to do this. Shameless plug
Check it out at
http://www.star-mate.com/lx200.htm and fire any questions my way!
Cheers