That is odd... I have just the opposite experience. I have several XTi 4000s and several XTi 2000s. At times I will bridge mono an XTi 2000 and run it for 1 EAW SB850 loaded with RCF 18 speakers, each rated at 1000 watts in 8 ohms. The sound is huge. I have also used the XTi 4000 with 2 EAW SB850 speakers one cabinet per side at 4 ohms 1200 watts a side and don't get near the punch. Are you sure the XTi 2000 is in bridge mono mode and that the cross-over is set as you would like it to be? If that is true then what your saying is exactly the opposite of what I have experienced.
I saw what U say about your expirience wit 2k & 4k crowns. I have 4 pieces 2k + 4 pieces 4k and I have tried so many aplications with all of 8 amplifiers,and have expirience with both models... In my system dsp on amps are allways in off mode.I allways use DBX drive rack for every aplication. Let me just say again my story: my RCF18 sounds much better with 650w@8ohms stereo on XTI 4000 than with 1000w@4ohms bridge on XTI 2000!!!!! !!!!! pls tell me are U using them in brg or stereo mode? My equipment is woking at EXIT festival ( if U heve heard for it ) & the festival crew is allways expecting as much dB-s as possibile... So few times I have pushed my amps in termal protect at night with outdoor temp about 10 C ( specialy with XTI 2000 ). As I said I'm new at this forum and I'm very pleased with your comment so let me THANK U 4 wellcome anwer 2 me. It would be nice if you send your Email to me so I can send U some photos of my system & some measurments ...