The best way, as stated above, is to indeed go to a shop and listen for yourself. That way I ended up with a pair of Genelec 8020A's instead of the much cheaper M-Audio AV-30, and i´m still insane happy with them!
Also keep in mind, if you buy a pair of monitors you also want a subwoofer.
I didn´t at first and i really missed the low sounds.
And for me the sub was more expensive than the pair of monitors.
I don´t know what your budget is, but if possible ask the shop if they can make a setup with a pair of Genelec 8020 or 8040, DynAudio DBM50 and Adam A7X or A8X.
I know those brands will give you quality for what you pay for. And that's what you want, right?
But remember, my hearing can be worse than yours, so it´s up to your own hearing wich pair of monitors is best for you