Raab some good advice here as always and very sensible comments form you.
Aside from the regulations, to be realistic and to sum up, so far as the real world is concerned you will almost certainly need some combination of VP prop., glass and under carriage.
You will also find the step up reasonably challenging so soon after your PPL - think in terms of 10 to 30 hours to be comfortable. On the basis that you will be hiring I would be surprised if you would complete the difference training and club / group approval on type in less than 15 hours.
There will porbably be some insurance loading as well.
If you are serious about a six seater and there happens to be any twins around you might consider them as an aletrnative. I think it is still 25 hours P1 time before you can do your multi but you might get your multi done in not a lot more than the minimium. (5 hours I think). The training will make you a much better pilot and will open up more options.
Like four seaters, six seats rarely mean you can carry six adults with reasonable amounts of fuel whereas in something like an Aztec you can load up six full size adults, full tanks and head down to Nice.