I need peace of mind when buying. You can't know everything about a boat, not even with a thorough survey by the most competent surveyor. There's always something about to break down, always something hidden trying to take your boat to Nature's original state. A better quality boat that is well maintained will increase the odds of not experiencing too much of that.
I understand your goal; I am not sure a more expensive boat will necessarily provide more peace of mind.
If you want peace of mind with an older boat, look for simple, open and sturdy from a reputable builder. Learn how to become an expert boat inspector, be selective about condition (does not necessarily correlate with price), and pay for every possible marine survey- boat, engine and rigging - before you purchase. Be demanding of the owner's knowledge of the vessel - don't deal with someone who is squirrelly, secretive or combative, throws out this caveat emptor
B.S., or thinks he or she is doing you a favor by letting you buy his or her boat.
Before you sign a contract, you should know why the owner is selling, the history of his or her ownership, and his or her knowledge of the boat's conditions, including all problems - and they all have problems. Any one who claims his 30 year old boat is perfect (except MaineSail), is either lying, ignorant or nuts.
The more complex, hidden and specialized the boat, the less meaningful interaction you have with the seller, the more likely you will have expensive problems. The less you know and the more you trust the owner, the more you are exposing yourself to costly problems down the road.
Given your needs, I wouldn't gamble on a more expensive boat. Any number of production boats would satisfy your criteria. Look at the problems the last boat you looked at had.