Good question… after I bought my car the first thing I did was get the all the wishbones refurbed, got the bushes replaced, got some decent suspension on it and fitted some braided hoses and pads - this was purely to ensure the car was all pointing in the right direction and was fundamentally sound. I didn’t touch the VHPD at all.
Then I drove it for a season of trackdays to get to know the car and improve my driving (getting used to no traction control/abs/servo’d brakes etc)
I think it’s very easy to get caught up in the modifying and we go headlong into it and justify the spend using man maths or by reading that someone else said the brakes were crap or that you need X amount of power etc…
I wanted to know that my driving wasn’t the limiting factor before I started looking at any increase in power…
I then did pretty much as Ben did, with gradual changes over the years - it’s now a very different car to what I started with… and at a guess is probably something like 10 seconds a lap faster around somewhere like Oulton park than it was when I started.
The latest round of changes I did were partly a preparation of the car to accept more power (bigger brakes etc) - but to be honest, now I’ve done them, the car is such a good package that I have held off going down the SC+CC route (and here I’d differ from Ben - I think if you are going SC, then you have to go CC too, just from a reliability perspective and to keep temps down).
With my car as it is now, I have all the driver involvement of an NA car, and can still manage to play with the SC+CC or 211’s/260cups - and it’s more challenging.
In a way it would have been nice to have a real solid reliable VHPD in the back… and I did look around for options at the time… there really just didn’t seem to be any evidence to support that it was possible - I’d still love to have a drive of a nicely sorted one (the Exige that’s in Oz that the guy did all the restoration work on looks lovely). But again, you are then looking at pretty much a custom ‘race’ engine rather than an off the shelf buyable commodity (same thing as a high powered Honda that we talked about already above).
I don’t think my VHPD was too healthy (it certainly wasn’t pushing out 190bhp) and the petrol fumes used to drive me mad… I wasn’t at all sad to get rid of it and put the Honda in. When I think of the strain the Honda has endured for the past several years it’s amazing really - it gets thrashed around and never misses a beat (touch wood).
In summary, I’d say that make sure your car handles and stops and that you can drive it somewhere close to its limits (not your limits) before you start looking at power increases (especially big ones!) - going from VHPD to Honda or Duratec isn’t necessarily a big power increase, and might actually make sense in order to get the car reliable depending on what your start point is.
If you go for big power increases and don’t have the skill to use it, I think you ultimately damage/limit your own driving progression - although you’ll sound fast in the pub/bar 
) using the stuff that has been proven to work. Indeed my car has lots of S/H parts that won races etc as part of their original host.