What you do depends on who you are.
Some people would trade in their 2012 Caddy because "it's old now."
Other people will spend whatever it takes to keep their car not only running, but fresh.
As an SVX owner it is up to you.
If you freshen up the engine, install new leather, steering wheel, custom paint, custom wheels you will have more money in it than
"the book would say its worth"!
On the other hand you would have a one of a kind, special, high performance, touring coupe, that you can be proud of!