Sundown has subs that will drop down low. However, most subs will when they are installed in a correctly built and tuned enclosure. I think you need to sit down and figure your budget and do not kid yourself about it. If you are content with lower power to keep from needing to upgrade your electrical then stay under 1200 rms and you have a ton of options. If you only want to budget 500-600 bucks then consider only those exact subs and amps.
Personally with a tight budget I would look at audioque. However, all options you are looking at will work out great.
That 10w6 is a torn down actually. I was messing around with it but I have had some interesting changes lately that has changed my focus a bit.