Gotcha. That amp should give adequate power to a sub. I think a 10" would sound great.
The car seems well-suited to bass. Maybe it's its shape?

As for Euro's volume settings:
I've had to turn the gain way down on my sub amp as well. That said, I'm listening to my music at around 5-9 on the head unit, w/bass at 0, and fader at 0. The gains on the amps are both well below 50%.

 

Anyone, about the KIT? Where and how much? 2004 Sedan non bose.

 

See the
https://g35driver.com/forums/showfla...&Number=231416
Thread.

 

WOW, $400 for the kit. HOLY ****!!! Oh well, I guess a HU is out of the question. I'm not really that cheap, but my god, that's crazy. If I get all this done and keep the stock HU and it sounds like ****, I'm gonna flip out!!!

 

In a perfect world we'd all replace our HUs, but such is not the case. I love where my car is at now. It sounds great. I don't have hiss, or alternator noise, etc. It looks stock. You keep the steering-wheel controls, etc. (yeah, you can rig an aftermarket deck to use your steering wheel controls if you want to badly enough.)
I bet someone will come up with a cheaper solution eventually, but, for now I'll keep my stock HU too.

 

Yeah, now that I have replaced the Bose door speakers, my system sounds awesome from the factory HU. I tweaked the level controls on the VEN4 so the signal is stronger, which made it sound even better.

The best part about using the factory HU is that even if you want to upgrade that later, you'll only be out the money you spent on the line output converter. It's worth a shot. I'm very pleased with the result with my system.