The OEM shock has a remote reservoir and individual adjustment for both compression and rebound damping. In my mind any replacement that doesn't have these features is a downgrade which eliminates the budget options. On this criteria I went for a Niton Track shock which I've been very pleased with. Nitron will set the shock up for you at the factory based on your weight, riding style and pillion requirements, they got this pretty much spot on in my case, I just had to decrease compression damping by a click as I have shorter dogbones which slightly alters the standard geometry. Also you can return the shock to Nitron for a full strip down and rebuild which I've just done after 4 years and the difference was very noticeable.