Hello just picked up a peavey classic 50..only have it a day..The enternal speaker jack is in the 16 ohm..theres also an 8 ohm rec...can i use either one.With out harming the amp.also when i add the 15speaker cab how do i set it up..410 in the 16 ohm and 15 in the 8ohm or the oppsite sorry for the lame question..thanks