First, as always, thanks to "atmasphere" for his input.
I would add that there are a number of considerations to address when buying a preamplifier. Connectivity being only one. Your system arrangement and placement of components is another important part. A good standard practice is to keep loudspeaker cables as short as practically possible. That leaves you with the interconnects. Any well designed & engineered single-ended preamplifier with a low output impedance (~200 ohms) should be capable of driving long runs of interconnecting cable. Choosing an interconnect cable shouldn't be left to chance.
For several years I used 30' runs between my preamp and my mono block amps with no hum or any other issue. My current arrangement in a new home is much different and my interconnects have stayed the same, but I just shortened them to about a meter in length. My mono block amps do not have balanced connectivity. If they had I may have tried both single ended & balanced interconnects especially if the amps were truly of a balanced design.
I would encourage you to home demo any preamplifier that you are considering before you purchase. Preamplifiers are a very important component in all things hi-fi. Afterall, it's all about the sound.
Happy hunting