Summary:
After replacing my midfi preamp (no name mentioned) with KRC-2, suddenly I can hear all the detail, it is so crisp clean. The musical instrument sounded so lively. I took a step further to see what made the difference in sound reproduction. Here is the result by using a function generator and a scope:
1. KRC-2 bandwidth goes beyond 10 Hz and 100KHz. My midfi is between 40 - 20k.
2. No significant phase shift between frequency 10 Hz to 100KHz. My midfi starts to see significant phase shift <100 Hz and >10KHz.
3. Square wave on KRC shows no significant distortion between 10Hz and 100KHz. My midfi shows huge distortion at 10Hz and 100KHz.
4. Noise level at quiescent, KRC noise level is 1/3 of my midfi preamp.

Conclusion: KRC is a true world class preamp.

Strengths:
Extremely clean, transparent, good sound image

Weaknesses:
Very costly

Summary:
An extraordinary pre-amp. Mine was bought new in '93 and is still used as a reference! It is extremely transparent, detailed and sweet.(probably due to the differential FET input stages) I have other Pre-amps etc but I would never willingly part with the KRC. The remote also controls Krell's monoblocks.
System :

Marantz CD-7/Krell MD-10 & Reference 64 DAC
Krell KRC
Krell KAS/Krell KAS2/Krell 250Mc Monoblocks
Hovland Gen II Balanced XLR Interconnects
Nordost Silver Shadow AES/EBU digital cable
Hovland Reference speaker cable
EW Andra's