Splitting line level out from preamp, versus using 2nd set of outputs

Why are you trying to run 2 amplifiers?

Wouldn’t you want a splitter with a female to two males?
Easy to find, like this one (link), but there are many for less money.
Typically, you would connect the splitter directly to your preamp and run the other two cables from there. I have done that to run a sub.

That should be fine. It’s hard to imagine the extra connection point and IC would penalize this enough to notice, unless psychological. 

So you’re using 3 sets of ICs to ensure symmetry between the 2 paths. That’s perfectly fine, but if it were me I’d probably look for an adaptor to work more like a "loop out" from the 1st amp, so I only need that 2nd IC set to hit the 2nd amp (if positioned close enough). The loop-out is used quite commonly on electrostatic headpohone amps (Stax) - and here, I’ve not noticed a penalty from using the loop-out. 

Of course you’ll find folks who are obsessed about the connector quality, and these can get quite expensive on the high end - I’ve been there in the past; now I don’t care so much. 

When "stacking" cables in series, with different brands or makes (especially copper vs. silver), the sound tends to be "additive" in the traits of the 2 cables. Like tube rolling. Which again, is generally fine IMO. IC sonic differences are generally pretty subtle to me, with exceptions for very long runs or specific slots like phono that can be sensitive to capacitance. 

Are you bi-amping?

A splitter made the sound worse for me. When I needed this same feature (amps), I purchased the CODA 07x preamp which has 2 sets of XLRs. This sounded much better than a splitter.

In my case, 1 amp drove speakers and the other amp dove my RAAL SR1a earphones.

Today, I use a Schitt Kara F preamp to do the same thing.

i split single outputs into an amp and a subwoofer. im very pleased with it. 

The OP is trying to avoid buying another 4M cable from the sound of it.  The Y connector should 1M>2F with the male plugged into the amp driving the high frequencies, and the short cable into the low frequency amp, assuming passive biamplification is the objective.  A preamp with dual outputs effectively has a splitter built in.

I would like to avoid buying another $$$ interconnect, and I’d like to leave everything where it currently sits (equipment on left side amplifier(s) between speakers.

i would be adding a second amplifier and bi-amplifying one set of bi-wireable speakers

Neither amp has a line level out, and those are some great suggestions to keep the signal clean.

I'm 76, over the many years, I've used Y splitters for this and that, and it's never been discernable to me or my friends that help me listen for any problems/differences.

I just gave an old 4 way Video Switch to a friend, he used it backwards to select between two TTs, works great, no more switching cables manually.

Dynacohum,  I think your idea is better than mine. As the signal runs it would hit a female rca at the start of my splitter.  Leg one and leg 2 split.  Leg one could be very short, and would end in male rca to connect directly to the high frequency amp.  Leg two could either be long enough to reach the low frequency amp, in which case it would also end in male rca terminations, or it could also be short, and in such case would have females on its terminus. 

Should have said Mulveling and Dynacohum. Great suggestions guys.

What if I plugged the male end of the Audioquest 1M to 2 F metal splitter into the back of amp 1, then ran incoming signal into one of the two F connectors, with the second F being used to feed the signal to amp 2?

Morrow audio makes whatever cable you need, splits, varied lengths, whatever connector you need.  They have a range of cable types for every budget, often having substantial discount sales. 
I’ve several of their interconnects and have found them reasonably priced and perform very well.  I’d avoid the splitters and get something made to suit without spending big bucks. 
apparently they’re currently moving their facility so orders are a bit delayed however.  
 

I have used rca f connectors off one amp into another and daisy chained multiple amps. Amazon ,parts express ect .good luck with your project and anjoy the music.f connector on the back oof one amp short rca to other amp.it is shorter than a y connector.