Hmm according to here and here the C has an extra pci slot , more usb ports, some extra audio feature.
But it also says the C has 100% All High-quality Conductive Polymer Capacitors. Hmm, because of this I think I'll have to change my recommendation back to h81m-c. h81m-c is worth 6.3k here (and probably in other shops at hafeez center as well) so its only a 500rs difference.
What does the polymer capacitors do? Sorry for these questions. I'm a complete noob. ._.