Well REW certainly isn't obligatory. It depends where you want to go and how much time you want to invest to get the last ounce of performance out of your room and your system. Its only a $100 investment (for the mic) and the learning curve is much shorter since Jerry published his excellent Guide.
But I would only suggest REW if you are also prepared to make changes. It's no use measuring and highlighting problems unless you intend to fix the problems you have identified. This can be as simple as relocating speakers and subs or as complex as treating the room acoustically. It is easy to fall into the trap of chasing ever smaller issues too (graphitis nervosa) but this can be controlled with help from the REW Anonymous Support Group ("My name is John and I am an audioholic...").
Personally, learning to use REW was one of the best decisions I have made in the pursuit of better SQ, but I have a dedicated room, where WAF is not an issue. HST, it is also a very small and difficult room, but with REW and the acoustic panels plus Audyssey XT32/Pro and a lot of help from AVS members (you know who you are) I have managed to get terrific SQ.
Keith they say admitting the problem you have is the the first step I'm about ready to take it to the next level, as soon as I add the second sub, I know I'm in good hands. I'd like to treat my walls somewhat, because I understand that would probably be the biggest improvement I could make, plus I have a GF that's into sound, and would jump at the chance to design some cool acoustic panels. She has a graphic arts background and it would be better than me making them because I'd make them all look like the members of Pink Floyd or bricks from the wall