hmm.. in my house, the record got M1310, E3100, M3300. so although some may not appear to be mine, i do test the sound.
I vote for M3300 as for clarity. you'll find many sharpness spoken by the satellites of M3300.... every people here know its the best in clarity in price range. however M3300 in some cases appear to be about 230.
M1310... not bad for its price. but if you do compare it to E3100 and M2300, sure no match, the price is only below 100...
E3100 advantage over M3300, M2300, M1310, M3310 and M3400 is that it has treble volume controller where all those Mseries have only vol and bass control. i've been in the same question with you last CNY but finally i manage to get myself a M3300. after a month of break-in, i sent it home and the sound is really2 good... (clarity esp.)
the best is you try it yourself. i remember last few weeks i was buying a M1310 for my friend. the good thing about the shop was i can try the speaker using my own MP3! well, i just plug my K800i in and listen. after a quick listening, i just carry it home and it sounds really good although i believe my X300 better (only 10RM differ).
good luck finding...