I always like Calibras, especially the Turbo model. However, now I see them and cant stand them. They are pretty damn fast alright, and although the FWD conversion has been made, Id much rather have the 4WD (although this does mean when you change a tyre, you change ALL 4 tyres at the same time - oh and the transfer box is the most fragile thing in Vauxhall history)
Id say keep your valver, and if you do want to upgrade to a turbo, either convert your own or go for an Impreza. Cheap as chips these days and very reliable, moreso than a Calibra, and with 4WD too
If you dont have the cash to opt for those, then stick it out with your clean dream!