Yes, the XLM in particular are much better than stock for the MRT.
Do Graz ribbons for Apogee sound better?
I bought Apogee Centaurus new in 1993, it is the model with the 8" woofer. I like them but am willing to pay for new Graz ribbons if they really improve the speaker. Mine still work fine. I am now using an Aloia amp from Italy, it runs class A, choke regulated in the AC, 60 wpc. Replaced a PS Audio 200 CX amp. Have David Berning TF-10 pre, Linn LP12 all decked out, Benz M2 cartridge ($1200), etc.