I would suggest a CD with a wide variety of material; A short piece featuring brass and strings for the upper ranges, another with a good kick drum and bass, another with panning effects for checking the imaging.
Try to pick out the individual instruments during play. Always take the specific speakers profile into consideration, specifically the design rolloff when listening to the extremes.
If you want to go so far, you might take an SPL meter to check the levels at various points in the range, as well as to establish a reference level (70 - 75 Db is generally good, but do a check at 95 - 100 to make sure there is no distortion (you might want to use ear protection at that point)) but also check with the speakers turned way down (dimmed) (this is where your familiarity with the material can be very important).
I recommend Alan Parson’s Soundcheck CD (this will have a lot of other material to check range and phasing etc., but there are a number of others available, or you can make your own. The recordings should be rather pristine - CD quality is perfectly good, but MP3s (even if burned onto a CD) are to be avoided. (The soundcheck CD can be purchased with a built-in SPL meter.)
Every room has it’s modes - even a “quiet room” so don’t let these fool you. If a given tone or frequency seems weak, move to a different spot (a few inches is usually enough) and it should get stronger. This is not a problem with the speakers but rather with the room acoustics. (Any room modes will also affect SPL readings.)