RE: JetCat P-90RXi details
If I had a P80SE then I wouldn't upgrade it to a P90RXi, especially if it was Kerostart.
However, I am currently building a BVM Mig 15 and I have all the parts (bypass/pipe etc) to fit it with a P80/P120. I did buy a P100 for it before the P90RXi was released but space is at a premium and the benefit of the simpler installation by having the pump under the cover, and also having the same mounting dimensions as a P80, mean that I will be using a P90 instead. The fact that the P90 is cheaper than the P100 is an added bonus.
I think the Jetcat range is quite good with a lot of the market covered; P20, P60, P90, P100 and P140 are all different and all have their pros and cons. If you want to upgrade a P80SE and want significantly more power then you can always go for a P140RX.