So anyways, i found this site to be my muse for a new little project and still have a couple questions before purchasing and installing. I was thinking of eliminating my head unit because it will cost another 150 to get a alpine Versatile-Link adapter to use the input features plus it frees up a much needed din space.

Right now i have an Alpine CDA-9851, interior infinity components, 1 JL 300x4 for interior speakers, and 500x1 for a 12" JL W6.
#1
Now, i can see how to run the inputs from the carputer to the amp for the interior speakers but i'm having trouble thinking of an easy way to separate the low signals from the carputer to the subwoofer amplifier such as the head unit sub preouts do. I know the alpine has a pretty nice bass engine, but i figure i can use equalizer software on the carputer to accomplish this.

I've been reading posts about people running subs with and without head units but havnt found exactly what im looking for. To get good input to the sub amp would i just send the full hi/low freq signals or is there a way to easily separate and filter these? Do i just use a splitter for the carputer sound output? How could i use the equalizer to control the bass in the interior speakers compared to the bass level at the sub amp? I know i can tweak the hi/low pass filters on the amps, but there is only so much i can do.
#2
Before i buy a mobo i'd like to know if anyone has seen any problems with slow video playback or sound quality using different mobos. I was looking at the via board and it looks nice but the p4 boards have options for faster processor speeds and ram sizes. Also i just caught a quick note about a nice looking AMD mobo, anyone had any experience with these?
#3
Anybody have any problems with bass affecting their carputers?

Sorry for the extra long first post, im still new to forums in general... I only found this site a few days ago but have been visiting religiously. If anybody could answer these questions here or redirect me to some posts that might help i would greatly appreciate it.