Help is this a speaker problem or something else.

I recently changed out my preamp from a emotiva umc1 to a Integra dhc 80.3 . I have listened to about 10 hours on new preamp, the amp I have powering the 5.1 set up is a Sunfire 200x. The speakers are Paradigm Studio 80v2 I bought new 16yrs ago. They haven't been driven hard just trurned up here and there. With this new preamp on certain heavy but fast recordings (CD playing) the speakers sound muddy or mixed up at higher volume like it can't reproduce the sound correctly or it's to fast the ( music) to respond and play correctly, loud volume but not near clipping, if I loose some volume they are fine. I never heard this with the emotiva that's why I wonder speaker issue or preamp, also I am listening in 2channel and front speakers are set to 40hertz rather than full range on emotiva,wirng is good and checked everything else sounds fine movies, pop, music etc. Any help would be appreciated. 
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The preamp is refurbished Integra dhc 80.3 , I just put in. I wondered what makes this type of music tougher for it to reproduce or get the signal there, it's certainly not all and ht sounds fine but if I could figure out I could return it just never heard that with the other preamp, or receiver I had previously, thanks for your reply