So 4 ohm DVC subs. So what I'd suggest is wiring the coils on the subs in series, then parallel the subs together at the amp. This will give you a 4 ohm final load. On that amp it makes very close to equal power between 1.5 and 4 ohms anyhow, but the damping factor and THD is better at 4 ohm.
Being a ported box you may want to check and be sure the box is within spec for those subs. I'm not exactly sure what you mean by "cracking" but an improper box will cause many problems.
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