RCA 5670's anyone familiar?

I have a 2 tube line stage with some stock Chinese tubes.
The sound is a bit harsh and bright.
I found some RCA's at the tubestore but the guy I talked to said he didnt know their sonic qualities as he seldom sells 5670's and has no customer feedback.
These are the only NOS 5670's I have been able to find.
Anyone ever used them?
Try www.tubesandmore.com, they have everything at great prices.
2 other sites for info (they can be pricey):
www.tubeman.com www.tubeworld.com
Hey Dave, why dont you call your pal Kevin....
Winoguy-have some more wine! :)
Great idea Dave!
Follow up:
I scored some NOS RCA matched pair of 5670's from the tube store.
Cheap too! $8 each and $10 to match them!
They sound real nice even with low hours.Smooth with no harshness or brightness like the Chinese tubes they replaced.