I don't think there will be many pres which have balanced outs but not ins. But so far I don't have a balanced source, so balanced ins are not currently a high priority.
Only reason for the balanced out requirement is the nCore which by all accounts sounds better when driven balanced, and that's the power amp I want to try next. I suppose I could use a balancing transformer on the single-ended outs of just about any pre, of course, but I'd like to avoid the rat's nest of cables that tends to go with bodged solutions.