Instead of tapping the speakers to the hi inputs, tap them into a PAC SNI-35 (or similar) hi-low impedance converter...
The Converter has inputs for left and right speakers, also ground (but you don't need them for the cobalt.)
It (obviously) converts the hi levels to low levels, AND, changes speaker wire to RCA cables to plug in to your low level inputs on your amp.
FINALLY, it's adjustable. You don't have to worry about crappy sounding bass!
I'll post a DIY within the next week, explaining how to install. I have a 400w peak amp and a simple 12" BAZOOKA 600w peak (piece of crap) sub, and it hits harder than three tens with 1000w in my old frand cherokee.
for less than $15
here
Last thing: Allow me to introduce myself.
Jack Metzel.
Orange County California.
Definitely a DIY'er.
Stock '07 LT1 (I think... It's definitely not an LT3)
13K miles.
5speed.
only mod right now: Subwoofer.
Mods to come: I don't even have any idea yet. But lots of stuff I'm looking at.