@fanotunes, Tim deParavicini's EAR-Yoshino electronics don't get much love here (though they do elsewhere, including at Positive Feedback by Robert Levi, and in the UK press, especially Ken Kessler in HFN&RR. Ken loves Tim's stuff), but his 868 and 912 pre's are designed to drive a 600 ohm load. Paravicini does a lot of work in pro studios (including Pink Floyd's), where 600 ohms is the standard.
Those pre's have no trouble driving a 10k ohm power amp input. They also are fine sounding, the 868L being noticeably better imo than the ARC LS-16 (I've had both). It had better be, costing over twice as much new, and twice as much used! It is a pure-tube design, the LS-16 a ss/tube hybrid (as are all the LS models). By the way, your RM-200 is called by some a hybrid design, because of it's bipolar input stage (the driver and output stages pure tube), which po's Roger Modjeski. But that's a story for a different thread ;-) .