Unsure. Which setup should I go for?

A few months ago I was going to buy two Audioque SD2.5 15's, but I ran into some financial issues and I haven't bought any subs yet. Now, I'm looking again and was set on the SD2.5's again, but then I kept reading great stuff about Fi.

I would also like to maybe go into a one sub setup just to try something new (I've always ran two subs.) So, I was thinking about either one 18" Fi Q, or an 18" Fi SSD. Either of the three setups would run off of a 1500 watt (or almost 1500) Hifonics Brutus amp.

I've done a search to see how well an 18 was for listening to rap but wasn't able to find any thing too helpful and I don't know anyone who's run an 18 to ask. And, I'm already pretty sure two 15's could get loud.

Let's see, I guess I'm asking for opinions on which of the setups would be best for listening to rap music, for bass of course. The sub/subs would be going into a Dodge Magnum so I could fit a pretty good sized ported box so space isn't too much of an issue, and again would be gettin almost 1500 watts.

I've narrowed it down to these two companies for the prices and because I know both are run by good people with great products and customer service.

Just would like to know what you all would think would be better for loud bass (it's dynomat'ed so I won't bother anyone but myself.)