Many good things noted already, so I do add only a little bit from my own experience. If you already are well trained on the Cessnas, I would advice to go Cessna. They are cheap, widely spread and when enroute, you will always find somebody able to help you.
First, forget the Cessna 15x, because you spend 75% of the money for a 172 at only 50% usability. Good mid-time 172s you will get for about 35+-k Euros.
Second, Cessna SIDs are troublesome, but Cessna was only the first to release such programs for older planes. Due to regulations all other manufacturer must follow on the "aging planes" rules.
Third, some maintenance organisations will rip your pocket empty for SID. Calculate between 3.500 and 5.000 Euros for a 172, plus things which might be found to fix. If your maintenance org does offer you a 15-20k estimate for the inspection, go for Hungary, Czech or Poland - there are some pretty good mechanics doing a great job on little money. BTW: my complete SID was about 6.000 Euros in Germany for a C172, including minor corrosion protection.
Forth, the SIDs are a good thing and even my Reims C172 had some surprises, we would never have found without the inspection. There was no dangerous area found, but a couple of things to fix now to get the plane ready for another 40 years. If you know corrosion is monitored, your feeling on the plane is better.
I am flying an old O-300 with about 27l/h Mogas STC and do derive a TCO cost monitoring. At 100h per year I have total costs monitored at about 190 Euros/h, with all buying depreciation, avionics upgrade to GNS430 and SID included.