Here's a fairly detailed picture of the BX2, and here's one of the MR2. You can see a couple of differences: the BX2 has the aerodynamically sculpted port opening to reduce chuffing; the MR2 appears to use a mass-produced one. The BX2 has a mesh dome over its gold-plated CCAM tweeter; the MR2 does not. Also, notice the difference in frame rings around the woofers. I checked the descriptions here and here, and the BX2 uses the new CCAM woofer where the MR2 uses an MMP II woofer, which is probably previous generation and less expensive. The cabinets have identical dimensions, or nearly so.
The list prices aren't all that different; MR2 is $399, BX2 is $489. I don't know what street price is for the BX2, but current Amazon price for the MR2 is $328.
The list prices aren't all that different; MR2 is $399, BX2 is $489. I don't know what street price is for the BX2, but current Amazon price for the MR2 is $328.