Any alternative to Radio Shack sound level meter?

Minorl, It is easy to see the problems but much harder to fix them.

Kijanki, don't feel bad. It always looks awful. When I show people what their system is actually doing they usually puke. Remember a lot of the variation below 150 Hz is room effect. If you move the microphone three feet in any direction it will look totally different. 

Kijanki all that is wonderful but now you need a very high resolution way of digitally creating mirror images of the curves then EQ on top. It takes at least a 64 bit system. The best way is with a digital preamp with room control and the ability to modify curves such as the Anthem STR and Trinnov Amethyst. 

I'm with Erik on this one. The are a lot of hand held dB meters on the market. I keep one on  my coffee table. I have room control and getting all that stuff out is a PITA. With the hand held I get an answer just by flipping the switch.
Using a dB meter to set up subs is difficult. You would need to impulse test very driver and graph the results. Using say white noise my not produce equal levels between the drivers. The best way to do this is turn the subs up until they are obviously too loud then start dropping the volume a little at a time until the sub just disappears. If the sub does not disappear you have a phase/time alignment problem or just bad subs.
I like my subs aggressive. I use a curve that is up 6 db at 18 Hz dropping to 0 dB at 100 Hz. This produces the air behind that kick drum strike which is very realistic. Check out a small jazz club. Brittany Howard's new album Jaime uses a bass drum without any damping what so ever. You can feel that bass drum head shake producing a glorious boom instead of a thud.