i need some help im planning on buying a 18 fi bl sub in the next couple days and im going to run it off a hifonics 1606d and i was wondering if i should go with a dual 1 ohm or dual 2 ohm?......

You would want to go with the d2 so you could wire it to run at 1 ohm to get the full potential of your amp.1600@1 ohm 1100@2 ohms,so your sub will see 500 more watts at 1 ohm.

i agree , give the sub the power it needs to perform, if you underpower , it might damage the sub

Underpowering will NEVER, EVER damage a sub.

How about something other than the Hifonics?

*hoping you pick a different amp*

If your amp is 1 ohm stable you need the dual 2 ohm for a single sub, if your amp is 2 ohm stable then the dual 1ohm coils for a single sub would work.

^^^^ X2

Underpowering a sub will NEVER hurt it.

And if you have that amp already it will work fine but the earlier hifonics amps did not put out rated power, as far as I can remember the 1608 and 1610 will do rated with good electric though.(I still wouldnt buy one)

Saz-1500D is all i have to say...