Dennis,
Thanks for your post. The older NAD used to have a switch on the bakc to optimize the amplifier for a 4 ohms or 8 ohms - the distrotion is a bit lower in 8 ohm mode if memory serves, and the RM25si 's are 8 ohm speakers, so if you go back for another listen see if there's a swtich on the NAD 370. Also NAD preamps have a "bass eq" button that can fatten the bottom end of the speakers - it's intended for use with smaller speakers, but it could be accidentally
deployed!
Anyhow, glad you enjoyed the RM25si's and good luck with whatever audio path you choose.
Jeff