Still in the hunt for a real UQ for the chilly Fall weather in New England! Due to moisture issues up here, I may bypass down for synthetic insulation in any UQ I buy.
I got the AHE New River with IX liner that I use, also have an incubator. I think you can go with a down UQ if you also add the Silnylon UQ protector from 2QZQ. You could even use one of MollyMac's IX socks to add protection and warmth to your down UQ. Lots of ways to do it without having to restrict yourself to synthetic due to conditions. I like having both the synthetic and down quilt to give me more options and use when I feel like it.