The TC-5200 subwoofers are engineered for small sealed, ported, passive or horn loaded box enclosures and designed for high power to ultra high power capabilities. Because of the high BL product, the sealed box volume virtually makes no difference on the frequency response of the system. In other words, there is not a box small enough which would house a TC-5200 to affect the response, therefore it's most efficient to build the box as small as possible. We recommend an amplifier between 1500 and 4000 watts RMS per driver
What exactly are you asking?If I was in a need for a space saving setup I would go with those subs for sure but that's still quite a bit of power if you ask me.
You can under power subs because nothing bad wil happen.Then when you can support/afford more power go ahead and supply it to the subs.The RMS rating on subs is just there so you don't go too crazy and blow em,at the rated wattage the sub will perform it's best is what the manufacturer is telling you.It won't hurt to under power though but it probably won't perform to it's full potential.
hd3 has build quality all day over an L7 and shuold be louder...if you properly power both (hd3 getting 2krms and L7 getting 1krms), hd3 shuold be louder