Thank you all so much for your continuing suggestions. I've run everything again along with doing the sub "crawl" and I'll post step by step what I did. The end result was lousy but I'll explain and hope for help at the end of this reply.
To correct my earlier post my room is approximately 1,722 cubic feet and approximately 198 square feet.
A few folks have commented on the amplification for my Kef mains. When I originally bought them, I purchased a Pioneer 49TXi which was at the time their flagship model and had 165W. I didn't even stop to realize that the Denon doesn't have nearly as much power. I went to the Crown by Harmon amp calculator and entered 3.048 meters of MLP to speakers, 88 db efficiency, 85 dB desired SPL and 15 dB amplifier headroom. This calculator gave a recommendation of 147W. My Kef manual recommends an amp of 50 - 200W. I'm not sure it's completely relevant to my sub issue but given your feedback, I may need to look into getting amps for my mains.
On to the subs:
I made all measurements at 85 dB based on my UMIK-1, using ASIO drivers for HDMI and using the SPL meter within REW5. My sub mode is set to LFE not LFE + Mains. LFC is off. LPF for LFE is at 120 Hz. My Left and Right mains are toed in and 10' from my MLP. My center is 8.6' from MLP.
Scale on all graphs are 45 dB to 105 dB vertically and from 15 Hz to 200 Hz horizontally.
Left Front PB13 Ultra Only
Right rear PB-13 Ultra Only
Both PB13 Ultras at same time (+ 3 dB combined gain due to dual subs - I did not change AV Volume or gain on subs amps)
Pre-Audy - Left + Subs and Right + Subs overlaid with each other
Now, I did the full Audyssey calibration for the MLP only. For the subwoofer level matching, I adjusted the gain on each sub to show 75 dB on the setup screen. This resulted in sub 1 (front left) trim of -9 dB and sub 2 (right rear) of -9.5 dB. The strangest thing out of the whole calibration that I noticed was that my mains crossover was set to 150 Hz while my smaller Kef 202c and Kef 201s were set to a crossover of 40 dB. I turned Audyssey to on and turned off the Dynamic EQ and Dynamic Volume features. To measure the Left Main + Sub and Right Main + Sub using ASIO, I select Output 1 for left (#2 for right) and Output 4 subwoofer for the timing reference output.
Dual PB-13 Ultras only
Dual PB-13 Ultras with left front main speaker with Audyssey ON
Dual PB-13 Ultras with left front main speaker with Audyssey ON - Waterfall
I'm really thrown off by the waterfall as it is substantially different than what I had previously. I used the default settings with 350 ms and kept the volume at 85 dB. Perhaps the change from 75 dB to 85 dB may have impacted this.
Here's a link to the full REW measurements:
Time to listen and evaluate
I put in U-571 as the depth charges are one of my favorite scenes for good bass. I set the volume to -10 dB and left the subs alone at their Audyssey defined trims of -9.0 and -9.5 dB. It was like there were no subwoofers at all. I then changed the subwoofer trims on both to 0 dB. While there was some perceptible bass - it was minimal and I know have had much, much better before where the room felt reasonably pressurized. I held my old school Radio Shack meter in hand and it was registering uncalibrated peaks of roughly 105 dB at the time. How can it possibly be that I have this sound level with what in this instance was now very little heard bass and virtually no room pressurization.
Something is seriously wrong and I just don't know what it is. While the waterfall now appears bloated, there still should be a feeling of some deep base in the room. In moving around in the room, I couldn't find a single good listening spot.
There is a silver lining - I ran a log sweep using the tone generator from 10 Hz to 100 Hz with a 20 second duration at 115 dB. Wow - there was some serious excursion at 10 dB. I really felt and heard the bass from 25 to 40 Hz and from 60 to 80 Hz. This leads me to believe the subs are working great and there is some other weird thing going on.
Thank you for your continued help in resolving this problem!