Replace Shock Absorbers or Not?

Hi
I currently have a 2006 RV Troopy with standard suspension. I have replaced the shock absorbers about 20,000km ago with Toyota shocks again. In the process of finding out about what was available after market wise, a suspension business that replaces all the police troopy and fire service ute suspension with after market products advised that they had next to brand new Toyota suspension available from these vehicles. The 79 series will fit the 78 so I am told and when I say next to brand new, the vehicles have landed from Japan and gone straight to this suspension place. I have obtained leaf springs,coils,hangers, u bolts, bushes the whole lot and there is not a scratch on them. Cost- free as they can't sell them as they are "second-hand" so they go in the bin. I will be getting this place to fit them to the troopy as my suspension has sagged a little and I like the idea of no extra lift as most after market stuff was 50mm lift or more. I would like to incorporate new shocks and have seen that Koni are good (and expensive) and Tough Dog Big Bore have received favourable feedback.
For those that have these after market shocks, is there a real noticeable difference with these as opposed to Toyota shocks?

Thanks in anticipation.

Cheers


Mark