New head unit and old amp- connector kit?

I know there has been a lot of discussion on this but I came across this link in my search for a solution:

Range Rover HC ISO to RCA Line in Adaptor online at Nexxia UK

I have the Alpine head unit and amp in my TD5 XS and want to swap the head (CD player also knackered) but want to keep the amp and speaker set up. There has been lots posted about bypassing the amp etc or plugging it in to the pre-amp sockets on the new head unit. Would the above link allow me to do that?

I have three sets of sockets on the back of my head unit and it seems the upper would be the right socket for the adapter from Nexxia? Ideally I want to change as little as possible so that when I come to see the vehicle I can return it to standard.

Any help much appreciated!

Scratch that! Rang Nexxia to order and was told that I don't need the kit as the amp is speaker not line level, and it is standard ISo input. Found an old head unit in shed, plugged in and all fine. Last time I take any notice of audio bod in local halfrauds....... Told me it would not work like that!