Weird Bass Reponse on my Speakers.

I just got a Talon ROC 2002 subwoofer dedicated mainly for 2-channel system. I tried to setup crossover point by using Radioshack SPL meter to find out what frequency that my Sonus Faber Extremas started to dip. I got weird results using Stereophile Test CD 1 (1/3-octave warble tone at -20dB). Here they are(SF Extremas only no subwoofer).

Frequency----------------SPL Meter Reading
1KHz--------------------->70 dB(reference level)
200Hz-------------------->62 dB
160Hz-------------------->63 dB
125Hz-------------------->58 dB
100Hz-------------------->52 dB
80Hz--------------------->53 dB
63Hz--------------------->60 dB
50Hz--------------------->70 dB
40Hz--------------------->61 dB
31.5Hz------------------->55 dB
25Hz--------------------->52 dB
20Hz--------------------->below 50 (unmeasurable by RadioShack SPL meter)

From the readings above,SPL readings started to dip at 200Hz(62dB) until it reach 52dB, which has the lowest value, at 100Hz and climbing up to 70db(reference level) again at 50Hz. And then I got lower dB as the frequency went lower.

So, I set the crossover frequency of my sub at 40Hz. and the SPL reading for lower-bass after combining subwoofer are:
(Upper Frequency responses are still the same)
50Hz---------------------->70 dB
40Hz---------------------->70 dB
31.5Hz------------------->70 dB
25Hz---------------------->68 dB
20Hz---------------------->54 dB

Here are my question:
1. Is the dipping between 63-200Hz and going up at 50Hz considered normal?
2. Is there anything wrong my speakers? Could it be other tube gears or my room that make cause this problem? (My listening room has no left wall at all)
3. How's your opinion on Lower bass responses after combining the subwoofer?

I'm pretty happy with the result musically but I think mid-bass responses might still be the problems for me.
My equipments are:
CDP: BAT VK-D5SE
PRE: BAT VK-5i (w/ Amperex 6DJ8 orange globe tubes)
AMP: BAT VK-60

Thanks for looking!