Do I need a fused distribution block?

Since your amps are fused on the amp, then you do not have to put in a fused distribution block. But like you said, putting them in will not hurt. Make the fuses in the distribution block slightly bigger than the ones on the amp so that only one fuse blows, not both.

And circuit breakers like the one you posted work fine as long as they are working properly. As long as you can push that button and it pops open, then it should be good. I've had one that quit popping open when the button was pushed. That is when you know you need to replace it. The circuit breakers are nice in that you can just reset the breaker once they pop open. Fuses have to be replaced. But honestly, as long as the wire is large and the breaker/fuse is large, it should never break the circuit. So if you can get a fuse for cheaper, then go for it. The breaker is only handy if the amps have a possibility of drawing too much power at max volume and you don't want to spend the money on bigger or a second wire.

And I'm sure you probably know, upgrade your battery ground as well.

In that pic, they used what were called ground distribution blocks. Notice how all the wiring is also the same color, and the installer used a magic marker to mark what is what...

I actually like having differentiation in power vs ground, just me I guess. a power dist wouldn't really take up much more than 1.5-2 inches of room and to me would look more organized than all same wire with marker showing what is what and 2 ground blocks....

Fwiw, since 1998, I have only blown a fuse three times...
1. punch 150 bridged to 2 ohms, blew all sortsa sh!t off the board, melted stuff, ground wire turned molton.... burnt a stripe across my hand when I went to make sure it was attached...

2. 4.6x, water ran down the back window of my 81 f150, best audio system I have had I think, sounded the best anyways, then again, I was young dumb and full of XXX and no money... Amp blew, rf fixed under warranty...

3. rf 500a2 (i think anyway, forget) just randomly blew some resistors off the board, was running the same rf xlc 10"s that killed the 150, as well as were pushed by the 4.6x... I got it fixed, cost was 125... Rf said not warranty and ran too low impedance, even tho was ran at rated specs...

Lent the same set-up to gfs bro, he some how managed to blow both speakers in less than 2 weeks cuz he is retarded and a dumbass I guess, blew both xlc's he sold the amp, I told him he had to give me 150... The subs were sluts and in 4 vehicles, still pissed me off.



I am rambling, sorry...

Anyways, all times I have popped a fuse were actual issues.

I would still run a power dist block with fuses ( as all power dist blocks are) and not just 2 ground dist blocks...

In the times listed above, the other amp and x-over network didn't die, I know that when stuff fails you can get issues with other items in the run if they aren't fused....
Or so I have been told, anytime I had multiple amps or other on the same primary I used a power dist block...