Time for Scopus?

[Diapason]

My listening room is a difficult space (20' x 9.3' x 8' with concrete walls and a cheap laminate wood over concrete floor) but GIK absorption has turned it from "unlistenable" to "not awful". Over time, I've actually reduced the number of absorption panels in the room, as I found using lots of them made the sound over-damped and lifeless. I now have about 9 or 10 panels (a mix of 242, 244 and monster), mainly at reflection points and behind my head on the rear wall, but with 2 behind the speakers at the front wall. I listen along the long axis, any changes thus far have been made by ear rather than measurement.

I recently moved the speakers further into the room (they're now about 4 or 5 feet from the front wall) and the sound has blossomed, with midrange and treble being better than ever and a real sense of space and life to the sound. However, it's exacerbated a REALLY sizeable standing wave problem and the associated bass boom at a certain frequency range. I don't want to move the speakers back because I'm enjoying the sound so much more in the new position, but at the same time when the problem note plays and excites the problem mode it's absolutely ridiculous.

Questions:
1) Have I any chance of taming this with more targeted narrow-band treatment, or am I expecting miracles?
2) Would the Scopus be a suitable thing to look at and if so how many am I likely to need?
3) I know I need to measure the room, but is there anything in particular I should look for to help isolate the problem? There's one thorny issue in that I don't actually have an easy way of connecting a PC to my system (no DAC, no pre) which adds a layer of awkwardness.

I've been skirting around the room issue for a while, but I feel it's time to try to improve matters if I can without breaking the bank. My system sounds better than ever, so if I could just tame this bass resonance (I don't need perfection!) I'd be happy.