Halo there, I have Krell KSA-150 with Krell KBL Preamp. I use DENON DCD-3500RG CD Player. All with ballance XLR support. I connected them with full ballance (XLR) for 1 full day, the sound stage is not as good as single ended (RCA) connection. I also have a Spectral MS One (old) preamp, I connected the Spectral preamp with Krell KSA-150, wow.. a lot of improvement. My sugestion is find a Spectral preamp, it sounds very good & your Krell will be more powerful. Just FYI Krell KSA-150 & KSA-250 is not fully balanced power amplifier. That's why Krell produced MDA-500, which is KSA-250 fully balance Power Amplifier. For full balance (XLR) connection KSA-250 will be a mono amplifier. If you have just one Krell KSA-250, single ended (RCA) connection will sound better, more focus, more resolution.