There are in fact two reasons I wouldn't part with mine. The first is that it's taken a lot of work, money, time and components to get it sounding like it does. I can't seriously see it ever not being at worst a serious backup here, but as it stands, the only things that have shifted it from prime position have been review stuff that's not in my 'justifiable spend' category.
The second, more realistically, is that all the internals are on the basis that I've done them as experimenting towards an eventual separate build. Even then, I'd most likely use it for parts, as the transformers are perfect and decent. It's been ridiculously reliable, but I wouldn't want it floating around with other people in future sticking fingers inside it, because while I know what I've done, others may not. Seeing as there's 1300 volts of raw DC in there, it makes sense to keep it.