The best won't be the cheapest, and the cheapest won't be the best. You need to decide which is more important to you.
The paint will very likely have faded on a car that's twenty years old, so if you just order by colour code, it may not be a great match, and different panels on the car may not now be exactly the same shade. If getting the best possible match is important to you, take the car with you to a good automotive paint factor, and they will mix the paint to match the shade it is now and put it in rattle cans, though you may have to pay a little extra for this service.