sundown fi

Currently I have 1 fi spy 15 in a 5cf box. I might be able to trade for 2 sundown x 15's and my question is which will get louder given the proper box for both. the sp4 is rated for higher power but I would have more cone area with the x's so this is where I'm confused. I just want to know if it...

Looking to buy any of the following: Sundown Sa-8 v2 -4 ohm only- quantity 1 or 2 Fi ssd 10" -2 ohm only- quantity 1 Fi q 10" -2ohm only- quantity 1 Please if the items are used don't expect me to pay near new price, I am only interested if I could meet seller somewhere in the bay area in...