Volume issues connecting Klipsch R-51PM to Audiobox itwo

I recently got the Klipsech R-51M studio monitors as a gift. Being a bit tight on cash, I opted to purchase speaker wire to 1/4 inch cables as opposed to buying a receiver. It appears that this has worked fine, but the monitors are extreme quiet and low quality in sound. Do I need to buy an amp for them? If so how would I connect that?

Also I'm very new to all of this so any help would be appreciated.