The lower impedance measurements (dcr? 3.3 ohms at what frequency?) you're noting are to be expected, particularly if you're comparing to "nominal" ratings. Burdening your amp with high current demands will result in excessive heat, and parallel wiring will reduce the impedance that the amp sees and thus increase current demands, so there's that. Heat is no bueno for the longevity of your electronics.
3.3 ohms isn't really that low for a fan cooled Crown amp, particularly if you don't blast it, but even if it works for now it's probably not something you'll want to stick with indefinitely.