I like both the Cardas and the rule of thirds (if you have room) for Maggies. Typically you would create an equilateral triangle between your chair and two speakers for a listening position.
BTW you have a near perfect room size based on a (very old) article in TAS - they mentioned 16 x 26 x 10 as perfect for hi fi in general.
BTW you have a near perfect room size based on a (very old) article in TAS - they mentioned 16 x 26 x 10 as perfect for hi fi in general.