There are just too many variables to get the absolute right answer. Each of us are different and see things in our own way. I guess you have started to look at your lifestyle etc. One premise you have got right is that new cars do not work financially well. We buy new occasionally still but it never is a good deal. The depreciation alone is murder.
I have a look at our total package about every five years. Then adjust major things if required. Minor adjustments are done as required on an ongoing basis.
Too many people do not calculate the inflationary component of future ongoing existance in a realistic way at all in my opinion. One size shoe does not fit all either. .
Personal debt usually indicates something is not right other than a morgage perhaps. You are fundementally somehow living beyond your means. Either restructure your existance or increase your means. Sounds like you are trying to restructure a little. If a morgage is absolutly required eliminating it as soon as possible usually pays off. Debt should be reserved for buisiness if required where it can be made to pay.
You drive about 12k per year. If you see that as almost a constant then you can possibly calculate your yearly costs. The cheapest should be a ricer as already mentioned with 70-100 k purchased right.
I picked up a clean toyota at a car auction at christmas time for 3500 with a little less than 100k. It is five years old with air etc. It should have about another 100k in low maintenance left in it. That would give us about eight years at 12 k per year. Or 400.00 per year in depreciation if we drive it out. Maybe 500.00 in yearly expenses other than fuel and insurance. Perhaps less as usually I repair things out of habit and enjoyment rather than utilizing garages. I think the older mercedes diesels cannot deliver quite as much fuel efficiency. Nor cost less to maintain. Especially if you farm out the required work.
My problem is in our family that particular car will see a lot more than 12k per year so proportionally our costs are higher and depreciation more rapid than your senario. Then again all life does not or should not rotate around saving money for old age. You have to enjoy life as you go along.
Today there does not seem much difference in 1,000 dollars when I was thirty eight and say 5,000 dollars today. If I had just saved money at prevelant interest rates or held it in marginal investments we would have more than likely lost ground in the last 27 years. Good quality assets have faired much better over time in our experience and in general do not attract very much tax.