I found them a nice upgrade. I also upgraded the fuses (Synergy HiFi). I would not call it night and day but a nice upgrade. I got the (Create) Synergy Hi-Fi 5AR4s too. Do a search here - there are threads about their tubes and reviews at 6 Moons. Not horribly price at $80 each. I also put their 12AU7s in another (Odyssey) preamp in a secondary system.