Any alternative to Radio Shack sound level meter?

The easiest I've used is a free download app called audiotools.  It provides a sound level meter and also real time analyzer adn fast fourier transform tools.

You can see gaps in your system and room.  I use the stereophile test cds and play pink noise or other signals to see where the system and room is lacking.

not complicated at all and quite easy and simple to use.

Not professional quality because you are using your Ipad or Iphone's microphone, but it works pretty well non-the-less.

enjoy

You are absolutely correct.  But, if you don't know what the problems are especially peaks and holes in your system/room response, you are stabbing in the dark.

but, you are right.  fixing it is serious business.  Room correction has got to be the most difficult mind numbing expensive experience.  not for the faint of heart.  The good thing is if you know the problems, it is no longer trial and error.  

enjoy