We would like to have incredible paella in Barcelona and then listen to Spanish guitar music (can be at a different place but at least close by) any suggestions? We will only be there on a Monday night.
Don't want to spoil your pitch but note that paella per se is not local to Catalan culture (it's Valencian) nor Spanish guitar either (it's Andalucian). Having said that, as cosmopolitan city, Barcelona also offers the chance to enjoy both.
For rice dishes, including paellas:
For Spanish guitar performances:
http://www.palaumusica.cat/en/programme_314 -check the program, some performances are offered thru the year
http://palaudalmases.com/home/en/ -this one is rather flamenco but might be of your interest too
Absolutely the best restaurant I have found in Barcelona: El Raco de la Villa....look for its website. Looks small from the outside, but it is very large, well run, and great real Catalan food.