D’Agostino amp with Spectral preamp

There shouldn't be an impedance mismatch.  If I recall correctly Spectral preamps can work well with non-Spectral amps, but Spectral amps should always be used with Spectral preamps (and interconnects).  Spectral believes in wide bandwidth performance which can unsettle some equipment.  Good luck.

Thanks guys for you input. Sounds like I should tread carefully here. 

Spectral designs are ultra-wide bandwidth and really optimized when used in a system wide approach with their matched electronics and recommended cabling. It's more than an attempt to sell more of their gear, but with the instrumentation grade circuitry involved the networked cables are pretty much a requirement for their electronics to perform as they were designed and maintain stability. You will hear some reports of users who match a piece of Spectral gear with other brands but that's not the way to get them to perform at their peak level.

@carey1110  

I used to have 2 pairs of D'Agostino Momentum M400 monoblock amps driving the Wilson Alexx at the time and was using the ARC Reference 10 linestage preamp at the time. They paired really well together between the Dag Momentum M400 monoblocks and the ARC Ref 10 preamp with the Wilson Alexx speakers I had at the time. I highly recommend pairing the Dag amps with the ARC Ref 10 or Ref 6 linestage preamps. Before using the ARC Ref 10 preamp I was originally using the matching Dag Momentum linestage preamp but I preferred the ARC Ref 10 pre paired with the Dag Momentum M400 monoblock amps on the Wilson Alexx speakers. They sounded better together IMO.