I've owned the Line 3 for about 3 weeks. I was in a stereo store last week and listened to a system with the BAT VK-50SE the big brother of the VK-5i. I'd say the VK-50 was dead even with the Line 3. Your concern about the noise floor is interesting. The Line 3 is the quietest preamp I've ever heard including the 380s Levinson. I guess the Ayre might be quieter but have only read the reviews. Buy the way the thing you need to consider is price. I got my Line 3 used on Audiogon for $2600, which included the registration card. So this demo unit (new) was a real steal. The Line 2 is a Stereophile Class A component and the Line 3 is even better.
