Zanon, you seem to feel that RTA has some intrinsic value. In any case, in terms of results, I think you already have a sense of where this is going. If you are bound to use your present speakers in a room you yourself deem too large for them, then I "recommend" that you basically forget about "loading the room" and tune the system so you can +/- comfortably wear your speakers like headphones. With some tweeters, one needs a layer of tissue, fine silk, or... to pull this off, and some attention to upstream matters may also be required.
Apart from DSET (only an option, not a recommendation), fully buffered, real time, multi-band equalizers are available on the 2ndary market (also an option rather than a recommendation).