I have two Xtant Amps run off the same 0 Gauge Wire. At the Amps, the 0 Gauge Splits down to 4 gauge for each amplifier. One of the amps requires a 120AMP fuse and the other amp requires a 50AMP fuse. Xtant amps are not fuse protected at all, you have to add them inline.

Do I add one fuse at the battery or one/two fuses at the amp 4 gauge split? And what size? They don't make a '170' fuse..?

 

200amp

 

I would put a 150 - 200 amp on the main line at the battery. I would also fuse each individual amp line with the proper fuse at the 4 gauge split. Or use some type of fused distrobution block, like this one:
http://images.cardomain.net/products...TRCBR44A_1.jpg
that I have a used one of for $30 shipped

 

I agree with rider.

And you don't need a huge distribution block. Here's the best pic I've got of the four into one stinger block I've got. (it's under the ignition coil)