As far as loud, they all can be heard from a block away if you turn it up, so that will be up to you.
As for sub brands, it would depend on what kind of music you listen to:
Rock and Rap= Kicker
Acoustic, Jazz, Chill music= Infinity
As for Head Units that accell at matching the interior illumniation are the following:
-Kenwood KDCMPV-5025 (entry level)
-Alpine (mid-grade)Tougher to find with Amber illumination, but can be found
-Nakamichi CD-400 (hi-end) Uncompromised sound quality, but not a lot of features.
As for that crossover, I don't see the need. Most amps will have all the necessary crossovers you need. And I don't recomend running an amp in Tri-Mode to push both speakers and a sub.