Hooking up 2 diff amps

[threebills]

So I'm hooking up a fosgate t400x4 which will be on 4 -2 ohm 6.5 mids and tweets,with a fosgate t1000 BDCP on 1 fosgate t1d415 (DVC) thats 1000 watts rms(fosgate always underated,even the amps birthsheet is at 1540 watts rms at 2 ohms).So,I know this is overkill,but I don't mind the money cause overkill doesn't hurt.Getting the big 3,and I'll have a 2500 watt cap,I'm gonna run 1/0 from the battery to a splitter,splitter will have4 awg pure copper to the t400(which will have at least 100x4 rms(about 29 amps)) then a 50 amp anl fuse to THAT amp.....then 2awg to the cap,then to the t1000 to a 125 anl fuse(or 100,not sure cause at 1500 it pulls 109 amps,prolly a 100 fuse say(which max is about 1500 watts rms,but prolly never even need it figuring the 15 maybe will run 1200 rms max on a deep note)so my question is.....about the grounds.....since the t400 is split on 4 awg and the t1000 is on 2 awg,should I just ground each amp with the gauge going into the amp straight to a chassis bolt?Like 4 awg ground for the t400 and a 2awg ground for the t1000? Or should I use a block?I was just gonna use the same cable gauges going into each amp coming out as a ground to the same spot.Or do i need to use 1/0 as ground for both amps being that's what i used before the split.I was thinksince it's overkill I could just use the same gauge coming out of the amps as a ground as goin in.Also far as the t1000 into the DVC 15 speakerwire is 4 gauge copper enough?or maybe go 6? Also 1 more question to add,since I have 1/0 positive from the battery to power splitter for the amps do I have to have 1/0 on the big 3 coming from the alternator to the neg of the battery? Thanks in advance for your help...this is bustin my brain a bit and I'm kinda ocd so I like to be perfect lol.