I am truly worried about this since I am eager to get a X10 or X12 and it has to deal with power issues.  I have an Arc Audio XXD 2080 and it des 240 x 1 @ 4 ohms when bridged.   I truly have been wanting to get a Fi Audio sub since three years ago but would like to know would the amp and the X10 or X12 would work together hand in hand or would it be a total flop?

It wouldn't be a total flop. You can always upgrade to more power later if you wanted.

Well there is a guy who is selling a D3 600.1 Diamond Audio amp that does 600 x 1 @ 1 ohm but the thing is he closed down shop and he is selling all the Diamond Audio amps for less than retail.   The Diamond Audio amp that he wants to sell me is $100 so I am debating on that since I am also looking into an Arc Audio or Zapco amp to.

power is power, you wouldn't be able to hear a difference between those amps assuming they're output is the same