preamp with two adjustable outputs??

I have not come across a preamp with 2 ADJUSTABLE OUTPUTS. Cajunpepe mentions the Macs - do they really have INDEPENDENTLY ADJUSTABLE outputs? if so, then you're in luck :-)

MY Sonic Frontiers SFL-2 has 4 outputs: 2xXLRs + 2xRCAs but they cannot be individually adjusted; i only use the XLRs at the moment but for a time did a bi-amp using 2 identical Musical Fidelity XA-200s via the 2 RCA outs. i have not used different amps or same amps but different power outputs, otherwise, i'd use a good x-over for that.

.e.

MBL 6010D has output adjustments for left and right channels for each of 2 main
outputs enabling you to "balance" the gain for 2 amps in a bi-amp situation.

"MBL 6010D has output adjustments for left and right channels for each of 2 main outputs"

Well that certainly complies with the OP's request for a "high end" pre-amp!!!