From personal exp with the LVL 4s I feel the AQs will handle more power than recommended better. My 18" was getting around 1200 1300w daily from a Kicker KX 1200.1 and I could get her a little stinky if I tried, (and I usually run my gains very low).
The Level 4s are nice subs, but I honestly feel even with the LVL 5 coils, the LVL 4XLs would be a better choice compaired to the HDC3.
Take it like this, the copper HDC3 and the DC LVL 4XL would both function very well off of 2k each, its been done several times by people on here. I would not feel comfortable giving a LVL 4/LVL 5 coils that much power daily, even though its rated at 1500w RMS.