@willyht what has your experience been?
Since I started upgrading my system from mid-fi to hi-fi 6 years ago it has been 100% Audio Research. I have been through 9 different preamps and 4 different amps. I always saw the biggest impact from amps with the preamps offering more subtle differences. The majority of these upgrades were with the same speakers. I tried a few different speakers along the journey but always sold the contender and stuck with the original.