room treatment

I have my system in a room which I am considering treating. I down loaded a program and entered in my room dimentions. Length-18 ft, res freq is 31.36 and multiples there of
Width-13.4 ft, res freq is 43.28 and multiples there of
Height-7.8 ft, res freq is 72.06 and multiples there of.

res freq was calculated by the program. I am limited with what I can do with the room because it is a rental unit. The right side wall of the room when facing the home theater unit has an opening 5 ft wide to the ceiling(7'10) . It also has a chase, approx dimensions , 16 x 24 , that runs floor to ceiling.Floor is carpeted,ceiling is spackled, large fabric couch and two fabric chairs, have four large leafy plants which I hope helps to deal with reflections. My system sounds relatively good but I can tell that it has alot more to offer. I will slowly be upgrading the system. I have Paradigm Monitor 9 mains with center and surrounds. 8"sub to be replaced. The rest will eventually go. Is there anything that could be done to improve the the way the room sounds. Bass seems to be the weak spot. Kick drums could come out cleaner. Can anything be done reguarding the res frequencies? Some input would be most welcomed.