I have entire suite of 6 ohm speakers (PSB Image series) that were coinnected to a lowly Technics SA-DX940 and now a Yamaha RX-V1800. Both of these receivers were able to crank the sound to loudness levels well beyond comfortable listening levels. The Tehnics started straining but the Yamaha being more powerful does this effortlessly. When I say uncomfortable listening elvels, I mean mid 90s dB sustained.
If the senstivity of these speakers are in the high 80s (87 or higher) then any midlevel recevier will have no difficulty driving them. By midlevel, I don't mean price wise, rather from a manufacturer's product line mid level. Avoid entry level, Hope this helps.