Here's what i would do. Get 2ga or 1ga equvalent from BOC Gases (its welding cable, costs $7 for the 2ga and about $9 for the 1ga) and use that from the battery to the boot, with say a 150A fuse about 12" from the battery. Then use a distribution block in the rear to your two amps (this cable to your each amp can be 8ga or 4ga if you want...that size cable is also available at BOC Gases).

The reason i suggest doing it this way is that then in the future if you get more powerful amps, you already have the cable there and wont need to re-run it or waste money on new cable. And the BOC Gases stuff is dirt cheap compared to the cable you buy in audio stores but does the same job (unless you done like the industrial orange plastic casing ). If i knew about it when i originally did my stereo i would have done it this way, and it would have saved me buying some of this stuff later on anyway and re running everything