ive currently got two sundown e8v3's and i thought about getting 4 more. these subs are very cheap and i have the room for 6. it would help for your input on amp ideas 2nd batterey? box designs.and would these be louder than sayy 3 12's? or 1 18?
6 - 8" subs would be more cone area than a single 18. I'm too lazy to look up the Xmax of the e8v3's so I'm not doing displacement calculations against common 18's.
I can tell you that 6 of any sub will get pretty loud, but it's all about the box. If I remember the E series should be good for about 350w per sub, so 350x6=2100w.
You would need to know your final ohm load to know what amp suits your needs, but you shouldn't need a ton of electrical besides the Big 3 and a better under-hood battery for "2000w on music".
Matt