With one child iso fix or non iso fix is pretty much a "meh" argument.
It doesn't take long to do the belts and just as secure. There's no point to doing both iso fix and belts as thats overkill. ISO fix are rated to a minimum of 18kgs so no need.
Sometimes it can be more hassle with isofix trying to line things up without damaging the seat - isofix "prongs" on the seat/base are sharp and will scratch or tear leather if not careful.
When using a group 0 seat with a base, the base is the only bit that held in with the belts so the ease of use comes from using the base rather than the isofix. Group 1 seats are handy to have as isofix.
When you have more than one then isofix comes into it's own as seat belt buckles are not well position for multiple seats. Downside... if you have three then the iso fix positions mean only two seats so you have to bin that and go for belts.
One issue with isofix in the RS4 is that the rear seats are reclined a bit which for a rear facing seat tens to make them sit up too far. Isofix have no adjustment where as you have a lot of wiggle room with belts.
Seat protector is a must - I used these
http://www.amazon.co.uk/dp/B0001WAO9O/r ... B0001WAO9O
- they are very tough so won't generate indents into the leather.
- allow isofix to be used easily.
- enough "overlap" to catch any... explosions.
But we used a couple old towels and a couple old catalogs for ages. Spare cushion works well for the larger seats.
No you do not need to notify insurance of using a non audi brand car seat.
it gets really complicated and expensive when you get to 4 kids but doable.
