Amp/Speaker ?

Just bought a new amp 2/340 watt...powering 2 audiobahn 8" speaker cans on the tower...The deck is currently running 4 stock speakers...Any ideas on the best way to power the speakers to get the best sound...dont know much about it..any help would be great

Also...system that is currently running without the amp...I am losing power when the volume is too loud or I trim the outdrive...This started after the new deck was installed...any help on this as well