What about Real Sociedad? I find them a very likeable club as well.
The big 2 basque sides(Athletic and la Real), Villarreal and Sevilla are all worth looking out for in my opinion. Real Sociedad have a lot of potential at the moment too, it's all about keeping the likes of Martinez(which I hope they do personally, as it's great to see players stick by a club in this day and age, although it's quite common from the 2 basque clubs to be honest) and Eusebio as manager and I believe we could see them in Europe again soon. If they lose Rulli also, then I think they should go back in for Bravo as he would revitalise himself there. San Sebastian is as good as his home.
As for Eibar(another Basque club in fact), they are effectively the equivalent of Morecambe reaching the premier league, before establishing themselves as a mid-table club. It's amazing what they have achieved.