Hi i can say that its no differens in buying a RER and convert it t REP/REW the units will be just like from factory and of course the units is preloaded with maps for yor country.
www.carperformance.se
So the cheapest way is to buy a correct can bus speed Mygig RER to your car and convert it to REP or REW and just plug it in to you car !the lowspeed Mygig RER sells about $450-$500 usd and the Highspeed sells about $650 usd!
We take 1099euro for a Mygig REW/REP and of course you have warranty on it!
All navigations that we sell have of course preloaded maps on it to your country and is plug n play installation!
We have a great service and mail support !