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 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