Meh, not a recommended grounding spot, but I'll let someone else get into that.
Custom sealed enclosure for your car correct? Custom meaning it fits in a corner perfectly like the JL Stealth boxes?
As for settings, they are all on one side of the amp. First there's bass boost, which should be turned all the way down/off/ to the left. Then there's your subsonic filter, which stops frequencies that may be too low for your sub to safely play, from reaching your sub. which I believe you don't need to be as worried with in a sealed enclosure. That said I'd turn it all the way down, to the left, then bring it to the right just so it's at 12 o'clock position. Then we'll get to your Low Pass filter which is actually labeled as XOVER FREQ on your amp. Note what position it's pointing right now, then turn it all the way down (to the left). At a half way position (3o'clock) it should be set around 110hz, which is more often than not, much too high, so you'll want to turn it down to a 1 or 2 o'clock position, looking to get it set to 80hz as a good starting point.
Keep in mind, these are just starting point settings, and that's just where I would start at to begin the trouble shooting process; any of these settings may need to be adjusted at any point to fine tune sound.
Most importantly, you'll need to purchase a DMM. That's a Digital Multi Meter. A cheap one can be had at your local Radioshack for $20. Not the most accurate or feature packed device, but it'll get the job done for what you need. Then go ahead and google "how to set your gains using a DMM" and follow the instructions. This is most important because if your gains are set too high, you could be sending a clipped signal, which will damage/destroy your equipment.
