So, if I am considering a Hsu/SVS/Outlaw ...

What is your budget?

What room restrictions do you have on the size of the box?

For about $1K you should be able to build a pair of sealed boxes using the Dayton 18" driver here:
http://www.parts-express.com/pe/showdetl.cfm?partnumber=295-472

And then power them with this amp:
http://www.walmart.com/ip/Behringer-Stereo-Power-Amplifier/17656014

This should give you plenty of output and extension for just under $1K (drivers, anp, wood, other materials, etc).

But there are tons of options based on your budget and cabinet restrictions.

I think the above suggestion is quite good.

Those (from PE site) are both terrible recommendations. 3 cu ft sealed is too small. 1.5" mdf is unnecessary, and two 3" ports are way too small. Down firing would be preferred.

2 15's would be better than 1 18 for evening response out in your room. Of course 2 18's is even better.

If you decide to build sealed you will have the deepest extension, but will give up SPL and require some EQ down low to realize that benefit.

If you build ported you gain some output at tuning. 14-17 hz is good and low but will still require a high pass filter.
Edited by nograveconcern - 1/16/13 at 11:41am

Forget the PE recommendations. You could absolutely build an end table type of design for these, but you might be better off doing with a sealed dual opposed style design if you go in that direction (end table) the dual opposed configuration will cancel out vibrations in the cabinet so you could use it as an end table. Something using the above Dayton drivers would be fine and would give you one end table for under $1K using the same amp above. See Gorilla83's thread on building a dual opposed box using the Dayton 18" drivers.

Or you could get four of these:http://www.parts-express.com/pe/showdetl.cfm?partnumber=295-190

And build two dual opposed end table subs. I am actually building four single cab 3.8 cu ft subs right now using these 15" Dayton drivers. I currently have an Hsu VTF-15H and the four DIY subs will offer considerably more output and extension for $1K than the Hsu.

If you have sometime, I would download Winisd Pro and model some of these drivers in a box:
http://www.linearteam.dk/default.aspx?pageid=winisdpro

If you want downfiring you could also do a Sonotube style design such as the one that Stereodude recently did. I would advice you to look through the completed subs via the sticky on this site and look for some box designs that make sense to you.

Rattle stuff on the table? It should rattle the whole room.

So you need to pick some speakers first. Then an amp, and then model the enclosure w/ some software.

A DO end table would probably be easier with the drivers facing the sides than up/down. You are going to need about 6-7 cu ft net for 2 15" DVC's or HO's. More for HF's, a little less for the new Stereo Integrity 15's.

What he said

The link I sent you to Winisd Pro will allow you to model some boxes.

This should get you started on what it is and how to use it (it is free):
http://www.hometheatershack.com/forums/diy-subwoofers-general-discussion/6330-winisd-pro-tutorial-download-detailed-guide-how-use-winisd-pro.html#axzz2IAhH0l7W

I was a noob too, but once I got the hang of using Winisd Pro and folks like nograveconcern helped answer my questions, things started to make sense. As nograveconcern said, you are looking at a 6-7 cu sq ft enclosure for dual opposed drivers, but if you are trying to minimize vibration, this is the way to go.

You can play around with this site to get an idea of how big a 6-7 cu ft enclosure is:
http://www.hometheatershack.com/forums/enclosure-volume-calculator/#axzz2IAhH0l7W

Something like a 24x24x24" box should get it done. You can go a little taller if you want the box to be more narrow but this will most likely be dictated by your sofa.

Other things to consider are material (MDF, Baltic Birch, etc). I would stick with 3/4" material for an end table and you have lots of options for the top (glass, wood, granite). Again, search around and see what other folks have done with subs as an end table.

Once you determine the dimensions, you can always take them to Home Depot and have them cut the wood to your dimensions for you from a full sheet of MDF or plywood. They will most likely charge you extra, but it may be worth it if you have not done this before. Then you need to cut the baffles for the woofers using a router and a jig. If you don't own a router you can either try and borrow one, buy one, or rent one. There is going to be some work on your part here to get this done, but in the end it will be worth the results as you simply wont get the same performance from a commerical sub without spending more money. Most likely about double.