Standing vs. Seated-Big Difference in Bass???

When you stand up you listen to a reflected bass.
You'll definitely need to either kill the reflections with room treatments or tweak the speaker placement closer or appart from rear/side walls.

You do not mention how far out from the wall your speaker's woofers are from the wall behind them. If they are not located at least 5.5 ft out from that wall, then I would recommend trying anywhere from 5.5 to even 8 ft out (measured from the woofer's front).

-IMO

Uh...also exacerbated by the big suckout in the upper mids/low treble when you stand up into the "crossover null" cancellation of the mid and tweeter, allowing your ear/brain to PERCEIVE more bass. Almost all the bass you hear is reflected energy, as the wavelengths are long and pile up weirdly, btw. You'll have to play with listening seat position as well as speaker position to arrive at a smooth response that provides reasonable bass linearity and mid/treble response that's not too affected by sidewall reflections, for example. Keep at it...the rewards are abundant!

You are in a bass node,a place where direct & reflected bass energy are "piling on".You can adjust speaker distance from wall behind them,your listening chair foward or back,bits of both and or add bass traps starting with corners behind speakers.I would start out with adjusting placements,which will take patience and time but cost nothing.Bass traps and room treatments should help in all areas of sound such as image focus and harsh or bright reflective energy.There are links to diy basstraps that are very effective and attractive along with other room treatments.You have just discovered that the "room" is a big factor in sound and of major importance to end result.

FOLLOW UP:
I must tell you all that I am unable to move the speakers no more than 18 inches out from the rear wall. Married here and well... you know?
As for seating position and speaker distances from each other I can/will...
Any other suggestions?
I love my Soliloquy 6.3's when I am standing but seated, different story, and I mean a BIG differnet story.
Thanks guys,
Bob