The A90 sounds just like what is it is being fed.
I owned the HRX for about 4 years and could never get rid of the slight leanness in the midrange, leading edge in the upper mids and lack of richness compared to my TNT V-HR.
Your Koetsu has been balancing that sonic trait IMO.
The guys are right, the A90 will breath better with more hours, however I don't think it will change that much, hopefully I am wrong.
If it does not improve, you might need to look at changing cartridges to a tonally richer sounding one, or change your turntable like I did.
I owned the HRX for about 4 years and could never get rid of the slight leanness in the midrange, leading edge in the upper mids and lack of richness compared to my TNT V-HR.
Your Koetsu has been balancing that sonic trait IMO.
The guys are right, the A90 will breath better with more hours, however I don't think it will change that much, hopefully I am wrong.
If it does not improve, you might need to look at changing cartridges to a tonally richer sounding one, or change your turntable like I did.