It depends on ur budget and someother factors. Mono class D are more efficient and u have 750W while ur subs need 500w so it's always good to have extra headroom for ur amps to keep ur gains down.

For option 1 u r talking about opting for a 2ch amp rt....a 2ch amp that gives 300W per ch at 4 ohm is gonna cost u a bomb and secondly these 2ch amps are not as efficient as class D means they draw a lot of current.

In my opinion option 2 is the way to go.