Opened a biggy here,
IMO if they were a factory option then no, others will say yes, I know one person on here that declared his RSTT's, Sat Nav and Bose sound ! which IMO is mental.
Most insurance companies will show that the value of the car is not to exceed £30,000 etc and from what I have been told by friends in the business if they were a factory option and the car was written off then the insurer would go to Audi and get the spec of the car from the factory if it was to be replaced. You could also say that you bought the car with them on and not being a car expert did not know that they were the wrong alloys. As said it depends on what they will cost to add to the insurance, Privilege told me that it would cost £160 more a year for RS4 reps that are £400 plus rubber to replace, where as the car as it is, the 17" OEM Avus alloys are £191 each plus rubber /ubbthreads/images/graemlins/crazy.gif so they pay more for the standard ones? the way they look at it though is that if it makes the car more appealing it will be more nick able.
I had a big smash in my 328i M Sport coupe at the end of 2002, it was not my fault and the car had over £5000 worth of repairs done to it, one of which being to replace the front left alloy as it was smashed, now I had 18" MV OEM alloys on the car, the model car I had (E36) came with 17" BBS Split rims, so quite a difference. Now the car was repaired by BMW and they swapped the wheel without questioning it not being standard, any BMW tech worth his wages would have know that the 18" MV came only with the E46 Sport models from 2001 onwards.
It depends as always on the individual condition, the insurer, etc etc. IMO if you are worried about it call your insurance company and ask how much to add them? if you think it is a good price do it.