It says in the manual that my Xtant 6.1 amp needs 4awg wire as a minimum for Positive and Ground inputs however according to bcae1's system design assistant 8awg should suffice. Would I still be able use 8awg wire? Or do the wire inputs only allow for 4awg?
You can use 8 gauge if you want. The power terminals will accept different gauges. Unless you plan on listening to the stereo loud, 4 gauge is not a must. However, if you can, you should use 4 gauge.