Best Balanced and singal ended pre-amp?

The Aesthetix Callisto and the ARC Ref 2 Mk2 both fit your description. I have heard both of these units in my own system. The ARC "asks" by a switch on the front panel what you are using at each input, single ended or balanced. The Callisto is balanced, and if you plug into the RCA, it is wired to accept that side of the signal without switching intervention. The ARC is remote control, a huge plus. The Callisto is a fully balanced (4 deck) stepped single precision resistor volume controls PER CHANNEL, making this one of the best volume controls in any preamp. The ARC is a single chassis preamp, making it easier to find space for your other gear. The Callisto is dual chassis, the main unit plus a separate power supply. You are looking at two exceptional preamps, I hope you will find a way to audition both of them, and see which one suits your sonic preferences.

I have a BAT VK-50SE and BAT sells output high-quality XLR-RCA and RCA-XLR adapters. The adapters don't result in any sonic losses other than not getting the benefits of BATs fine blaanced circuitry. I don't consider this to be klugey. The 50SE is a fine preamp and you can't go wrong. Also, I may be selling my BAT VKP5 phono pre soon. This may be a good option.

Don't overlook the BAT. I own it.. and have both single ended and balanced source components going into it. The VK30SE has both XLR and RCA, but the 50se with the connectors is just fine...much better preamp too...