STL

Ok I looked up the lvl 3 and the skar vvx. They look like good subs. The price range on them is similar to the SSD and the SSD takes more power. Im not stuck on Fi. I like DC and other brands 2. But out of those three subs I'd say you would be happier wit da SSD overall. If you get them stick to 1krms (Unless you kno wat ur doing)You should be good with your electrical.

When you say demo u mean like (burps) Or daily playing them no more than 5 minutes to show off? If ur answer is the 2nd choice and your going with a 4th order it will be loud with the SSD's. And if you plan on not playing them for more than 10min (Demos only) you can double the power (Make sure its clean & unclipped) and if electrical & install is right, U could "Possibly" see early 150's. Mainly late 140's. And with those amps your going wanna get a couple mo batts & another alt. Dnt 4get to do "Big III" on vehicle, and use 0 guage. What is this going in? And if your going with Fi what are your options for the subs?

Yes that is to small u would be choking the subs. The best thing to do is 12-14cuft after displacements. Do you have that space? Whats your vehicle? 12-1500 is ok but I wouldn't recommend it. The SSD takes 1000wrms and 2-500 more watts wouldn't make a difference in sound. U would have to put at least another 1000 watts on each sub to see a db increase. But I wouldn't put that kinda stress on a SSD (If u dont know what ur doing). 1000wrms for each sub will be plenty doe. U would be impressed (Especially if this is ur 1st time with 18's & Fi Audio) but other than that what is your goal? what amp or amps do you have in mind? do you have the power (Alts, batts, wires,etc.)? Whats your budget? Do you want a SPL (Daily) or a SQ setup? Get back with me! "Hope This Helps"

Were just trying to help you out. Honestly if u bought those you would be disappointed and the output you would be getting. They would most like blow in a month and you wouldn't hit over 140 if that. Your better of getting 1 or 2 18's such as (Fi,DC,SSA,RE,AA,Incriminator,Sundown ETC) any of those choices I listed above will take up almost have the space and get 10 times louder than the 18's you have in mind. The cheap route is not always the best way to go (Especially with car audio). The guys are right. Dont get them just 2 say u have 4 18's while one dude has 1 and its twice as loud. That would be very disappointing. Just take this under consideration. "Hope this Helps"