It sounds like you have a travel time that allows you to really settle into a place. I assume you also enjoy that kind of time. This is quite a bit different than the typical advice and manner in which people here travel, hence the suggestion for only a night or two in Toledo. I on the other hand, think the ability to spend 4-5 nights there would be fantastic. It is the kind of small city where you can really relax and explore at your leisure if you enjoy that. It has several smaller museums and sites that are worth seeing if you spend more time there. The restaurant scene there is not as good as I have found in other places, so be warned if you also enjoy good food. Madrid is a short ride away to enjoy some of the highlights there.
Girona would be a good option outside of Barcelona. It would afford a few daytrip options too, such as Figueres to see the Dali Museum.
Cordoba is another small city, like Toledo, that can really be settled into for several nights. Another city with lots of winding Medieval streets to explore and some smaller, off-the-beaten-path museums that daytrippers and one-nighters don't see.
But be forewarned that none of these options are small towns and Toledo and Cordoba can get very crowded (like Bruges). There are plenty of small seaside towns along the Costa Brava outside Barcelona - Cadeques has been mentioned and Sitges is another. Cadeques is better with a car but has some beautiful scenic areas nearby. Sitges is on the train line with links to other places like Tarragona (Roman ruins).