Run by a friendly guy (Eric I think) and company, the Parisien Hostal (114 La Rambla, 100m away from Liceu Metro station) has got an excellent mid-Rambla location opposite the Virreina. Its 12 simple rooms are well-kept; a double w/o shower costs ~4500 Ptas. However credit card is not accepted.
Accommodation near the north end of La Rambla may be noisy but atmospheric; others are darker but quiet.