batsbrew
without a corrected room, anything you buy in ANY price range is subject to lying.

Before I bought the ARC 2 system, I had a go at correcting my room with some EQing.  I was astonished as to how much I was listening to my room rather than the music:
 

 
That's a stack of 3x parametric EQs working together in series.  You can see cuts of around -15db!  Unfortunately, you can't correct a room by working solely in the frequency domain; time domain effects also need to be corrected.  However, even that basic approach enabled me to produce a mix which translated quite well to other playback systems (e.g. my hi-fi).  It was this that convinced me to buy some more sophisticated correction software.
 
Getting the bass end right is probably the hardest problem to solve; do you go with ported monitors which have a flatter response until around 50 hz of so, below which the response drops off a cliff, or non-ported ones which have a less flat, but more even roll-off all the way down to very low frequencies?  Another issue with ported monitors is that, in response to a musical signal (as opposed to noise which is often used to produce frequency response graphs), any spectral content at the resonant frequency of the port will tend to ring on for a short while.  They'll have more than just one resonant frequency too.  Do you incorporate a sub to compensate?  Bass frequencies also require a different room correction approach (the corners of the room as opposed to 'flat surfaces', i.e. walls and ceiling).
 
There are other factors too, e.g. the combination of horizontal (tweeter) waveguiding and the nature of the crossover can cause comb-filtering effects, especially if your listening position is not on-axis and at exactly the same distance to both drivers.
 
Given the combination of room, monitors and ears, absolute truth in what you're hearing is effectively impossible to achieve.  The trick is probably in reducing the lies to a non-preposterous level and (as others have mentioned) 'calibrating' the room by listening to good, representative reference mixes.