This won't apply to just Nissans, once you get past cookie cutter you really need to do your own research. Not 1 box/person will be the same for these custom jobs and the cost sky rockets. Are you a good woodworker? That'll help. Study car audio sites...etc so you can learn the specs needed and what not. Only once did I have an "extreme" system in a pickup truck and it was more problems then it was worth...
1. Small chips in windshields quickly cracked from pressure.
2. My rear suspension broke. (was the old school small nissans, which were popular "mini" trucks)
3. Had to upgrade alternator, battery and install a big *** capacitor - otherwise lights basically went out with a heavy bass hit. People would think I was flashing them otherwise cause they would at least dim. All those upgrades helped. (still, probably around 600 dollars just in those three, in the 90s - cost more now)
4. System sounded better with windows cracked, way too much sub (3 12s) for the small cab space of a pickup. My bad.
5. Truck was broken into 3 times. 2 times minor damage due to long *** screws used...etc and the alarm I guess helped. 3rd time the mother f'ing thieves ripped every wire and destroyed them. Although nothing was stolen, the system was wortheless since nearly every wire would've needed replaced.
6. Due to 5, paranoia was high so a lot of times I would not even listen to it anywhere near the level it was built for and would've been better off with a little system.
After the 3rd time though, I pulled it all and have never done anything similar again.
Anyway, be ready for some hassles and do a lot of studying/reading/learning. I was enlisted at the time and paid people to do all my work (no shop) and it was still stressful with design and all that. Good luck though.
Oh, sometimes you're better off just working with a local shop you trust. Hell, even franchises like car toys can have talented people on staff - they'll just charge waaaay too much and you'll never benefit from a relationship there. I found smaller shops, with high end locals in it give and take and appreciate your business more.