Wiring with distro block multi amp setup

New to the site, did some lookin around but haven't found any clear answers. Anyway, I'll get right to the point. I have a 2001 Grand Prix GT, adding a single 12" Kicker CompVR w/ an MTX Thunder 421D amp. Sub: http://www.crutchfield.com/S-ge3avUYWfe5/cgi-bin/ProdView.asp?g=520&I=2065C12VR4 Amp: http://www.crutchfield.com/S-ge3avUYWfe5/cgi-bin/ProdView.asp?g=520&I=2065C12VR4 Planned on getting my wiring from KnuKonceptz. I plan on adding a 2ch Kicker amp for some coaxials I plan to put in my front doors (again, during the summer) so I want to run 4ga from the batt. to the trunk into a dist block with 8ga outputs. Here's what I need to know... does it matter what size fuse I have up at the battery so long as it's ABOVE the amps rating (I have the MTX amp hooked up, it has a 40A fuse rating, does it matter if my fuse at the battery is like 80, or 40?) Now, distribution block, if I get a fused block, do I put a matching fuse in the block by the output of the amp it's going to? Ex. MTX amp is 40A fuse, should the fuse in my distro block for the output going to the MTX be 40A no more no less? What size fuse at the battery, what size fuses in the D block http://knukonceptz.com/productDetail.cfm?prodID=eKo-K4 w/ this block: http://knukonceptz.com/productDetail.cfm?prodID=BC-3448 There's the kit I want to order, I know I'll have to get some 8ga. wire to run seperately from the block to the amp, but that's no biggie. What does though the RCA cables w/ built in turn on lead mean? I don't need to connect and run a seperate remote wire to the amp? Confusing me cause I've never heard of that.