extending power wire

Right now, I have my power wire running along through my door jamb, which is not what I want. I want it to go through the firewall...but the current wire isn't long enough, so I would need to splice it with another wire to make it long enough...

How would I go about splicing this? Would I have to splice it with another fuse, or is there something else that I can use?

my wal-mart amp kit came with a splitter to divide your single power cable into 2 for a dual amp setup. I use that to "extend" the power wire from the battery to the amp in my blazer.

On ebay you can get a power distribution block for 10 bucks.

Dist. block or another fuse. Id think you would need more wire to run it through the door jam, than straight through the firewall. I think the piece that sickcallaway was talking about was the dist block.