which alpine amp 340 or 540

Ok i'm looking for a new 4 channel amp. I already have two mrd 500's so i want another alpine amp. Right now i have fusion comps in the front and plates in the rear but i'm changing to alpine comps type r in the front and alpine co ax type r's in the rear..which amp should i use...its a hundred dollar difference but will i need the extra power...i'm planing on making kicks for the type r's if that makes a difference..and they will be 6 1/2 in the front for the comps. thanks in advance

can anyone help

I would go with the 540

any reasons why...also i'm thinking about going with three type r subs 12 inch dual 4 ohm with my 2 mrd 500's would that work i really don't want to get a third amp for the subs