Oh there are so many to choose from. The majority of hotels and apartments are very nice. Use sites such as booking.com and have a look at the visitor ratings.
If the rating is anything near 9, the place is awesome. Last time I was in Grand Catalunya or something similar. Roughly 120€ per night, a roof-top pool and bar.
It was in the gothic area. Pure awesome hotel.
And yea, don't stay near the stadium. There's nothing. And I wouldn't stay on Ramblas either, but already in the Gothic area it gets a bit different and it isn't as loud
or crowded anymore. Another option is near the Universitat etc a bit north from Ramblas. It's a relatively nice area with many good restaurants and away from the
biggest masses or tourists.