Hifiman5 - I have the exact same set up as you - basement, carpeted cement floor and two 2Wqs. Funny story: In an effort to get a box of spare bathroom tiles off the floor, and having very limited space for storage in my home, I put the fairly heavy box of tiles on top of one of the 2Wqs. I never thought it would improve the already incredible performance of the 2Wqs. I will have to do some comparisons with and without the box of tiles.
And thank you, Johnny R., for the tip on leveling the subs. I know that leveling is essential for loudspeakers, but I didn't realize it could make a difference with subs. When my back is feeling strong, I will give it a try.
Man, I love the A'gon forums!