By the specs I am pretty sure 2 of those subs would definitely handle that amp, but I think the amp would start going into protection since the pair would be showing it a 1.5ohm load and the amp is only stable to 2ohms. With impedence rise you might be safe running the pair and kicker amps are stout but I don't know too many that are 1ohm stable (ZX2500.1 is the only that comes to mind and it is rated fro 2ohm only)
Too small of a sealed box will give you a punchy sound lacking in the low end extension. This is of course depending on just how "small" the airspace would be for the pair.
For a sinlge sub you would definitely be pushing the limits of the sub, most likely doable but you'll have to maintain some control in the power application (think overfueled diesel towing) Also the box size actually factors into the power handling of the sub as well. A smaller box will generally handle more power until you reach the point of the thermal limits of the sub.
So single sub wired to 3ohms will be seeing 450w RMS vs its 300w rating. This I think would be fine, you can keep the gain a bit conservative to tone back the power in this case.
Pair of subs wired to 1.5ohm would be seeing approximately 350-400w per sub but the amp will be pushing its limits. I believe at 1ohm nominal it will jump straight to protection at any normal listening volume but you JUST might be able to make it work at 1.5ohm.
I guess to give a straight direct answer I think I would go for a single sub setup in a box just a touch small like 0.6 vs their 0.625 recommended.