I am in the process of building an AR on DD's website but am unsure if I should build their MK18, V1, V3, V5, V7 or Tornado series and due to my lack of knowledge on the firearm and having issues telling the difference (outside of cosmetically) between them. This will be a home defense/range gun so I do not need the top of the line but want something that is customize-able, reliable and is quality. Any help would be greatly appreciated!