Sundown 1200 or 1000. Im a sundown guy. Very biased. So yea.

 

Price per watt ratio I'm going to say Alpine has JL beat to the punch.

JL is nice clean stuff but it's definitely a bit overpriced. You may also check out Rockford Fosgate for amps their T series is really nice. Alpine is comparable though, IMO.

 

A cheap box will defeat the purpose of upgrading the amp.....most of the output from a sub is box dependant. Find out what the manufacturer recommends for the sub you're looking at....if it fits in whatever amount of space you're willing to give up, its all good. If the shop you're dealing with simply tells you a box they have is "good enough" it probably isn't. It will work, especially if it is a sealed type enclosure but you will not be getting all the output you could be from the sub. The problem gets worse with a vented enclosure which must be a closer match to the driver specs in order to function properly.

I always suggest 3/4" MDF at a minimum for a sub enclosure....5/8" will also work but will flex more if it is not braced correctly to prevent the walls from flexing at higher power levels.

The JL boxes are well made and the correct size for the sub if that helps.

Also I would ask the shop for an upgrade to a 4ga wiring kit...if you decide later to add a second amp to power your components and/or coaxes you shouldn't need to run new power wire again which just adds to your costs later.

HTH