Planet Ms a cool place with all the latest audio video CD/DVDs. Both Indian and western titles are available in these stores.
But not all of their branches are worth visiting. Many of the newer ones are just small stores which have just a handful of latest CDs and some accessories like t-shirts and handbags. I think, the best branch in Delhi is at South-ex II. It has a very big collection of music with lot of different categories like pop, rock, class, country etc. You can also listen to some of the discs there. Its the best music store if youre looking for some uncommon or old music group / album.
They have a PlanetM card which aint useful until you spend lot of money on music Cds. You get points on purchase which can later be redeemed. Same like petrocards.
They sell only original CD/DVDs and the quality of accessories is also good (so is their price!!!).