JOSEPH, your concern about getting "upside down" in the cost of upgrading your beautiful car is well founded. I advise Whoa! on the temptation for new paint and uphostery. If you don't love your 'Lectra yet, expensive finishes are not going to carry you over the threshold. Enjoy your ride the way it is and revel in the thumbs-ups, all the while keeping an eye out for a voluptuous '50s replacement.
As for the driveability of a '64 Electra versus a '53 Buick Roadmaster, for example - no contest. Sorry, the older car is a stop light slug by comparison. For that you can blame the Dynaflow but it doesn't explain away the wandering steering that follows every dip in the pavement or the plan-well-ahead brakes. 'Fifties seats are sofa comfy and SUV upright, though, and luggage capacity is much better under the '53's big squarish bustle. Driven sedately, both cars with get you about 15 miles per gallon around town. The '64 might hit 20 on the highway, if you don't spend a lot of time in the passing lane.
From what I hear, older Buicks may have more trouble with the ethanol-diluted gas that the US has saddled itself with. You have to go looking for gasohol in Western Canada - but then we are sitting on an ancient lake of the real stuff. Not to rub it in but I heard a news report yesterday that, due to drought conditions, corn fuel is now more expensive than gasoline. Kind of like diesel - it wasn't supposed to go that way.
Once you've got the basic mechanicals sorted, a '64 Electra will provide you effortless driving pleasure. 100 miles to visit the folks? No problem and you'll be using less gas than your lead footed brother-in-law in his Escalade. The feeling of bigness will quickly fade away, particularly when you're parked next to his tarted-up Suburban. I used a '65 Coupe de Ville as my winter beater from 1994 to 2002. It only felt over-sized when trying to negotiate Tim Hortons drive-throughs, which I could avoid unless my three kids were with me, lined up in their child safety perches across that cavernous backseat. Man, I miss that Cadillac.
Your ginourmous Buick with its rocket-glow instrument panel makes me smile, which is what old cars are really good at.