I have had both ProAc Response 1 SC and Meadowlark Kestrel and Verio in my system with a CJ MV 60. They all work well with tubes. Each has its own strengths depending on what you want and expect. ProAc is more detailed or maybe brighter than Meadowlark. Meadowlark has a different sounding bass, maybe more bass. Midrange on both are close, with Meadowlark being a bit warmer. ProAcs are very stand dependent and Meadowlark need at least 6 feet between them to really image well.
What is your budget? There are options based upon price, music preference and the rest of your system.
What is your budget? There are options based upon price, music preference and the rest of your system.