Hi Bob,
That's a great question and I just got an email from a fellow with the same question, so I thought I'd share my response with him here as well:
First, I'd like to point out that a Birch Dungeness can pair with an Orca Deluxe; the Birch Dungeness has the same exact tuning point as the bamboo and the construction is the same (meaning, you're not going to hear the differences between the two cabinets like with the Orca Classic v. Deluxe and the price difference between the two subwoofer choices largely reflects the difference in material cost and machining).
I understand the preference to not have an extra cabinet for the sub, but we also have a lot of customers using the Dungeness tucked away under a piece of furniture and out of the way.
The extra clarity of the midrange and high frequencies is why you'd opt for the Deluxe. The Deluxe makes slightly better quality bass but a barely measurable difference from the birch.
The Orcas go down to 75 Hz, so they do great with light and hard rock for example, but the weight of the bass isn't as prominent. Even some of the ultra low bass is slightly audible, but again, just not as present.
So adding a Dungeness is going to not only up the frequency response (down to 35Hz - or, an octave extra of bass) but also is going to add presence of bass, so yes, it is a noticeable addition. If you don't classify yourself as a "bass head" though, the Orcas alone might do you quite well, and the Deluxe has better definition in this area than the Classic.
I hope that helps clarify things a bit more, and maybe some Orca and Dungeness owners can chime in as well with their opinions.
Cheers,
Clark
