Hi Mike,
No expert advice from me, since I still haven't finished putting all the components together to do any "real" testing, but I'll throw out a few thoughts.
Just like everything else in A/V, I always seem to need just a little more/better/quicker/faster/stronger/louder/etc. stuff to get the job done. I started with the Avia disc and a Radio Shack SPL and figured that was all I needed to setup everything I had. It probably was, but then I saw the graphs everybody else (it seemed) was posting, and I downloaded the free version of TrueRTA to see if I could do that, too. Since those results were a bit disappointing, I have since purchased the Level 4 True RTA, a Behringer ECM8000 Mic, Behringer UB802 MIxer, and I'm still waiting for a USB sound card for my laptop. Explaining all this to my wife sounded just like talking to my mom 40 years ago ("...but EVERYONE else has one").
Do I really need it? Probably not. The results from a basic SPL setup would probably be OK. But for me, the audio setup and tweeking is part of the fun of this hobby. Actually, I'm amazed at how inexpensive it is to put together enough parts to make a decent analyzer. The last spectrum analyzers I used were $25K - $30K HP's, so a couple hundred dollars seems like a bargain.
I know there are practical and accuracy reasons for using these tools. But for me - armed with the RTA, BFD, and Room EQ Wizard, I think it's going to be a lot more
fun to go do battle with the acoustic issues in my new theater (if I ever get it built
), than with the SPL alone.