REW is really not that complicated. We offer correction values for the RS meters so that they will be about as accurate as anything else in the lower range.
The initial setup is almost a must to know what your response is. An 80Hz tone at the same level as a 30Hz tone will sound faint. Trying to figure it out by ear is all guessing. Regardless though, most do have issues somewhere in the low end that can use some correction. It is always nice to know if what you choose to use to correct is actually working or not... and there just ain't no way to do that without at least getting an initial setup gig for 100 bucks or less.
A couple of things to keep in mind. Acoustical treatments are generally going to help more from 80Hz on up... and even then it takes some serious treatments to effect that 80-125Hz area. Below the 80Hz mark, electronic equalization devices will usually give you more bang for your buck. If you cannot afford the SVSound SubEQ, then forget the SMS-1, because you want find one of those for less than $500 or so... maybe a little less used if you get lucky and find one somewhere. Still... with any of these, there is a learning curve of some sort that you are going to have to deal with. It is actually a bit fun once you get to tinkering with it though.
You can upgrade your receiver, sure. The 876 is a nice one... the one I actually own. Those things seem to have gotten a bit high lately... from an authorized dealer that is. I may sell mine reasonably if you want one like new at a good deal, with warranty. I have been looking at the Denon 4310. At any rate, you can buy one and use the MultEQ XT, but you never truly know what it is doing and if it is helping unless you measure it.
