6SN7 to 6F8G conversion for Cary monoblocks?

Having read several audiophiles' enthusiastic comments on converting from 6SN7s to 6F8Gs, I'm seriously considering giving this a go for my venerable Cary monoblocks. However I am daunted by the need to use tube adaptors of un-reviewed origin and perhaps questionable quality. eBay is festooned with Chinese/Hong Kong versions of these adaptors from $10 each up to $34 each: Lee Moom, Suzier, Lowther Club, etc., but I struggle with perching $200 worth of vintage tubes on any of them without endorsement from the Audiogon brotherhood. Thoughts guys?