Technically you do not 'need' matched tubes but as a pratical matter there is little down side as most dealers sell new production tubes matched. If you want to match tubes for your amp, a matched quad for each side is optimum. You just don't need an octet, it will provide you with no extra benefit and depending on available supply might be harder to obtain. If you buy spares buy matched pairs and replace both tubes in the curcuit in which the one tube failed.
