I always recommend that you stay with identical tower speakers since dis-similar speakes do not sum efficiently. After doubling the power and doubling the investment, when you combine a conventional speaker with an HLCD (which has more output and a decidedly different response curve) you're left with only the output of the loudest speaker (perhaps just one dB additional output based on a six dB inherent difference of the two).
If you try to gain balance the two with separate amplification, then you're either bridling the dominant set or overdriving the weaker set. Keep in mind that a 6dB gain difference constitutes four times the required power.
This would also hold true for similar speaker types but of different sizes.
There are exceptions. If your objective is to aim the outside speakers outside of the wake for a much wider dispersion pattern then these two sets are not going to sum their outputs down the center axis anyway. But I still recommend identical types.

David
Earmark Marine