As owner of a Cambridge 640p phono stage, I'd say that it will outperform the majority of phono stages in mass-produced receivers. It may be a closer call with the phono stages built into ADS and Tandberg receivers, but those are hardly mainstream.
Also, the near-same-priced Parasound ZPre doesn't deserve to be mentioned in the same breath as the Cambridge. The ZPre sounds about like you'd expect of a $150 unit; the Cambridge sounds more like a $500 unit. In other words, there are a lot of receivers where you wouldn't hear an improvement with a ZPre, where you would hear an improvement with the 640P.
The 640p's s/n is shockingly good. This results in a paradigm-changing improvement in low level detail, frequency extension, clarity, imaging, soundstage, and dynamics.
Given that many online vendors have a 30-day evaluation period and that return shipping would be less than $10 if you don't like it, the risks involved in undertaking an extended evaluation of a 640P are very low.
Also, the near-same-priced Parasound ZPre doesn't deserve to be mentioned in the same breath as the Cambridge. The ZPre sounds about like you'd expect of a $150 unit; the Cambridge sounds more like a $500 unit. In other words, there are a lot of receivers where you wouldn't hear an improvement with a ZPre, where you would hear an improvement with the 640P.
The 640p's s/n is shockingly good. This results in a paradigm-changing improvement in low level detail, frequency extension, clarity, imaging, soundstage, and dynamics.
Given that many online vendors have a 30-day evaluation period and that return shipping would be less than $10 if you don't like it, the risks involved in undertaking an extended evaluation of a 640P are very low.