compared to the L5, i'd say the L7 15 would be much better, but i did have two L5 12's before and they got loud, but if i had the chance to get a 15 inch L7 over it, i'da done it anyday of the week, especially with that zx 1000.1
iono about the 2 l5 12's but i got a single l7 15 the 06 model with a massive audio rs 100 amp powering it but its only pushing 760 watts which isnt enough and i;d say its pretty loud even with that amp imma upgrade to a kicker zx 1000.1 or a kicker kx1200.1 so it shud be a lil bit louder and i created my own box too so prolly wasnt a good box as well since it was my first box i ever built ported
Just compare the actual RMS wattage and at what voltage on the kicker to see what size you are getting. I have one and it seems to work ok but the wattage drops a lot at 12v with car off, though other amps can also.
I'd look into Atomic,DD,RD or Stereo Integrity.I wouldn't buy anything from Fi until I know they're reliable and durable and that's why I don't recommend Fi.