Let me preface this - I am not a sparky either - but be careful with Jaycar power supplies. I had the same concerns in powering my G11. The advice was to use a slightly higher voltage so I chose a 13.8v non-switch mode PS (I believe these give a cleaner output) from Jaycar - this one:
http://www.jaycar.com.au/productView...UBCATID=999#12
This I used to power everthing that was 12V - my mount, focuser and ccd camera. Seperately I hade a powered USB hub (5V) and, of course, the laptop (connected to the mains). Of course all the equipment is interconnected via the USB shield. Result? Fried my Sbig CCD.
The reason I believe - not a sparky - was not a ground loop but the design of the PS - it had a "floating ground", that is the -ve terminal is not 0v or earth grounded (despite the metal case and 3 pin plug) - all you can be sure of it the difference between the terminals is 13.8v - in my case once this 0v was connected to the laptop 0v via the USB - smoke. I now keep all the equipment isolated.