Yes this is exactly what I experience and I don't like either M filter, especially the apodising upsample. It sounds very phasey and unreal to me. The non up-sample one is more real to me but lacks dimension big time. In fact it's so 2 dimensional it's driving me to look elsewhere for a music server system.
The only thing I haven't tried is the 818 as a preamp. I'm waiting for some new power amps to give that a go.