Hi,
I have owned two pairs of 3/5s and heard the AVI and VA. Your description of what you are looking for sounds to me just like the S3/5s, except that the bass is not quite flat to 60 hz. Particularly since you are already a Quad owner, I would think you would like the 3/5s, because the small Spendors have a Quad-like sound to my ear. (I have heard the newer Quad ESLS and owned 57s.) Other option as mentioned above -- look for a pair of LS 3/5as, but those are getting pricy. I also like the AVI, but it is a more forward, punchy sounding speaker, more resembling Linn Kans that LS3/5as. I only briefly auditioned the Haydn once or twice, but I personally didn't find it quite that engaging as the other two speakers.
TLH