Upgrading factory bose system w/ Eq

I have a 2003 Tahoe with the "standard" bose system, not the "premium". Its sounds good enough, but I want to add my sub and amp to it. THere have been plenty of posts on how to drive the amp using signals after the bose amp and they all have the same basic outcome... Crappy sound. What if I used an EQ like the Kenwood KGC-9044 with 2 preamp inputs and 3 outs (1 being a sub) spliced in between the deck and the bose amp? That would help to fine tune the sound from the bose amp and speakers as well as give me teh sub preamp I need. Any help would be appreciated.

Also I am not sure if I should use and EQ or a crossover. I want to have control over the bass so that I can turn it down or up when I need to without messing with the mids and highs.

I hate premium sound systems but I purchased the vehicle used and really had no choice. My goal is to retain the factory deck (it has rear audio controls so my kids can listen to something else) and its less tempting to steal. But I want aftermarket quality sound. I know... I may be asking too much. If I could just get the bass to sound as good as it would from an aftermarket deck I would be extremely happy.

Thanks for any help offered.

There's nothing wrong with getting signal after the bose amp, as long as you're using a good line out converter, and you're getting it from the right place.  That means if there's a factory sub, you need to go there for signal.  It's possible to just splice some RCA's onto the line level signals before they go into the amp- just use a harness for a reference if you don't know the colors.  Then, just use the crossover built into your amp.

I wouldn't recommend trying to integrate an EQ to tweak the signal between the factory deck and amp.  You may be able to sample signal from the factory deck, to provide a sub signal to your aftermarket amp, but I'd just use the amp's controls instead.

You said you want to be able to control the bass independant of the mids/highs.  You can use the bass controls in the factory head unit, and you can also install a bass knob inline on the RCA's (like the PAC LC-1).

From my past experience, getting the signal for my sub amp after the stock "premium sound" amp never sounds quite right. The bass is mushy and never seems to hit right. Actually, I have never really been able to get great bass (what you would get from an aftermarket deck with a dedicated sub preout) from a stock deck. That is why I was wondering if nayone had comments about adding an electronic crossover between the HU and the factory amp. If it splits and conditions the signal as an aftermarket deck would then why wouldn't it give me the ability to have the great bass I would expect from an aftermarket HU? It was a thought and I was hoping it work well. I really can't stand factory amps in cars.