A prebuilt box like you posted might be fine, but they always have limitations. The wiring out from the relays may be to small for the accessories you want to power, and it may not be easy to change that.

I was going to go with the Cooper Bussmann 5 relay / 10 fuse box at first, since it is a quality piece, has a water resistant gasket and can be wired to your liking.
That's not a complete solution though, you will need to buy the mini relays and fuses, and also the terminals and crimp tool for those. So it becomes more of a custom project but it's way better quality than the $20-30 relay boxes you can find from China all over ebay/amazon.

All in on a box like I linked above, you might be around $150 with the crimp tool, box, relays, fuses, and probably wiring as well. There is a massive write up on how to build this box here, DIY Bussmann RTMR Fuse Block, Part 1 ? Introduction | Bodenzord

 

Wow, that was an amazing write up! I can't thank you enough! This may take me awhile to complete, but I definitely want to do it right!!

 

I hate to keep asking more questions, but I think I've just about got this figured out except for one last thing. After I complete the fuse/relay box build, what wires would I then run from the back of the rocker panel? I wouldn't need all it comes with correct? The way I see it, I looks like I would only need a ground, power in, and the dimmer for the switches. Is this correct? Thanks again for all of the help.

 

The rocker wiring really depends on the circuit being switched and if the switch is illuminated or not. Since you mentioned a dimmer wire, I presume you will be using illuminated switches. In that case you will need a power and ground just for the illumination. If you only want the rockers to be lit with the other instrumentation, the dimmer could provide this power. Multiple levels of illumination get a little more complex. Then you need the in/out of whatever you are switching. For relay triggers, the power or ground used for illumination could be used for the switched relay trigger so only one wire to the relay would be needed. I prefer ground switching (providing ground from switch to activate relay). If you provide switched + to the relays, do not use the dimmer power, use a deticated +12V source.

To add to the previous question about all in one panels, there is nothing wrong with using separate components. SB integrated separate fuse and relay panels together nicely. You could even use individual relays and inline fuses; its just not a clean installation and good luck remembering which relays go to what when they are all in a bundle zip tied together.