Much depends on your room really. Could you give us an idea of room size, shape and acoustics (is it a well-damped or reflective room?) Also how close to the back wall do you have to site your speakers? Are you looking for standmounts again?
The BX2's are front-ported, but many other speakers aren't, so bass issues may be something to be careful about if changing speakers.
Is there anything about the sound that you feel needs improving? Just be careful with 'upgrading'. I upgraded to MA Golds a while back but actually preferred the speakers from the ranges below. If you like the MA house sound, you could take a look at MA Silver 1 or 2. There are plenty about used, particularly the predecessors the Silver RX1 or RX2. They use similar drivers to your BXs but have much improved cabinets - they're beautifully finished too. But they are rear-ported.
However if you don't actually like the tonal balance of the BX's, then there's little point in sticking with MA, in which case the advice to just go and demo some different speakers is sound.