They all can be heard far away in the right enclosure, but the most, I'd say the Kicker L7 (I hate Kicker and I will say why, but im giving my true opinion) The reason is it will shift the most amount of air, more then the Alpine and the Fi SSD, However Kicker L7s suck because all they're good for BOOM BOOM BOOM and no Sound Quality, a Alpine Type R 15" Will hang really really close behind a Kicker L7 in terms of SPL (Sound Pressure Level) and have much much, much better Sound Quality and Requires half the power the Kicker L7 needs. I've never actually came past a Fi SSD So I can't say much about it but judging from the companies reputation and the specifications of the subwoofer I would Probably say Its in the same league as the Alpine Type R, But will take more Power.
If anything, I reccomend you go for the Alpine Type R, Its best bang and Sound Quality for the buck, However If you want to follow the rest of the kiddies who want to blend in, get the L7, If you want to take it to the next level, The FI SSD is probably better then the alpine type R because It takes more power, thus hitting higher DB's, But I wouldnt because its more Expensive and the Alpine is at a good price. If you want to go with the FI SSD, dont settle for second best and go for the 18", otherwise get the Alpine, You could probably get two Alpine 12s for the price of 1 SSD.