Best type of Sub to consider?

If mainly for two channel I would go with a sealed design ...but I would try it with your speaker ports plugged and unplugged.

onhwy61 - No choice, I do not have two closed corners anywhere in the house, except one tiny bedroom. What you see, is my only option. One advantage to this setup, is that my detail has gone up a couple of notches. Subwoofers were recommended by my Horning dealer, but he does not sell them.

Dan - Thanks, Yes my forward firing option that I had mentioned, was based on the JL Audio subs that I was checking out. However, I'm trying to avoid brand recommendations, and get down to the physics and applications for the different types of subs.So, regardless of brand name, does one firing direction have an advantage over another or not. And, which one would work best in my setup, if any? That's all I want to know.
Kenny

I agree with ricred1.
 A sealed design will provide better bass accuracy than a ported one.
Looking at your room, have you considered adding acoustic treatments?

Kenny my experience with subs is rather limited as well. I am satisfied with my passive 15" Tannoy and Crown amp, and an old Velodyne that I removed the passive radiator, used a new Eminence 12" driver and 500 Watt plate amp.

This does what I need (I think I've brought this up before). Bass is clean and musical, the Tannoy passive being a great match for my Tannoy main speakers. You'll just have find your way the best you can, I'm sure you'll get there in the end. 

It seems to me that the answer may depend on where you would want to place the sub(s), which in turn may depend on how much of the bass region you want to augment. And given that all of the woofers in your speakers apparently fire mainly toward the rear, and that essentially half of the area that they are firing toward is non-reflective open space, I suspect that you would want the augmentation to extend relatively high in frequency (e.g., perhaps even upwards of 100 Hz).

If so, I see only two placement possibilities that might make sense, both requiring two subs.

One would be to place a sub alongside the inner surface of each speaker, firing toward the wall just as the woofers in the speakers do. (I presume placing subs alongside the outer surface of the speakers would be unacceptable because it would impede traffic, and perhaps also for aesthetic reasons). Although I would have some concern about the vibrational effects that placement might have on your turntable and electronics.

The other possibility would be to place the subs against the wall, one at its left end and one at its right end, with them firing forward. Ideally the subs would be chosen to provide a means of introducing a variable delay of a few milliseconds into their outputs, so that their outputs could be time aligned with the wall reflections corresponding to the outputs of the woofers in the main speakers.

For either of those placements, and if my suspicion is correct that you would want to augment up to relatively high frequencies within the bass region, it seems to me that two front-firing subs would be the way to go.

Good luck. Regards,
-- Al