Hi again

I have recently been thinking about buying new main speakers or amplifier, but as I read through reviews and articles I see that many recommend trying to do something about the room acoustics before buying new equipment (which sounds reasonable

). The problem is that I have not much knowledge about it and how to figure out what to do to improve on it.
So I thought I would take a measurement on a larger frequency range to (maybe?) help in figuring out how to make the improvements.
I tried measuring to 10kHz, but I was in doubt wether to use check levels with subwoofer or main speakers, and fullrange or subwoofer for target level. I ended up using the same settings as when measuring the sub. The graph I got is very unstable at higher frequencies.. is the graph making sense or am I doing something wrong?
I hope it's okay that I ask again
Here's the graph:
15hz_to_10khz_2.jpg