Kolossus Kable = Oversized, 8 gauge is really 7AWG, the 4 is really 3AWG etc...
eKo is more the norm/standard size, comes with less speaker wire and not as fancy an RCA Cable. For a basic sub install the eko is fine. If you MIGHT ever ad a second amp 4 gauge should be considered. If the total draw of the system is over 50A you will want to step up to 4 gauge.