Splitter -- One preamp to two amps. What to use?

I need your help! If people are bi-amping, How are they connecting from their preamp to their two amps and to their speakers?

I am currently running my NAD 1700 preamp with two separate outputs. One is a Lab unfiltered RCA out which goes to my Mid’s and Highs into one of my NAD 2600 amps. And I have a second RCA Normal, which is lower fidelity which runs thru another NAD 2600 into my woofers. I then run two sets of 10 gauge Blue Jean cable to each speaker. What I would like to do us upgrade my speaker wire ( AudioQuest Redwood or DR Acoustics Red Sky Bi wire ) which are bi-wire cables and bridge my amps to achieve 450 watts per channel.

Here is the problem. In order to do this I need to split the one output from the Lab RCA on my preamp to feed the two separate amps. I am currently using Audioquest Waters and hate to put something inline that is a lower quality than the Waters.

I can’t believe I am the only one with this problem. How are the smart audiophiles addressing this problem?