Sub Question. One higher quality sub or two lesser quality? (Rythmik vs HSU)

Also consider the possibility that "upgraditis" could set in if you go with the 2 lower priced/lower performance subwoofers especially if the higher performance/priced sub was within your financial reach. In that case, it would be wiser to get a single more expensive sub first as it would save you cash in the long run. After you get the 1st sub, skip a burger a day and save the cash for the 2nd one 6 months later. It does require patience.

If you feel that you won't be affected by "upgraditis" too soon, you could go with the dual HSUs. "Upgraditis" is a common disease among audiophiles (reason for this comment).

First, why do you want to add subwoofers.  Second, why wouldn't you go with open baflle subwoofers?  The GR servo subs are around your price range if you're willing to build the frames.

Come on Oz, you know the answer. Right? You have read the DBA threads, right? So you know that with subs more is always better. Right? And they don't have to be the same. And the more you get the less it matters what and where they are. Right?

@onhwy61 

You may have been looking at my system profile. I no longer have the X3s. I now have Cornwall IV loudspeakers. Even though I know they aren't doing much below the mid 30s, the bass they have is excellent. I am just looking for something to augment that lowest octave.

Oz

Check out that pair of Omega Speaker Systems Speed 10 subs here on the gon.  They look pretty interesting.  If you have walnut cornwalls, it might be a good match aesthetically