context is key…
I have used biamping as a boost to audio quality, but as Xanthe already listed - there are other ways forward that might make more sense…
I can imaging scenarios when a builder designs a rig to run, with improved sound quality (/at a lower total pricepoint) and from the ground up is ‘ready’.
reworking a bunch of bits to make this work doesn’t seem like a great pathway forward.
for me: bi amping was for ‘being a uni student’ and having the best audio I could muster.
with entry level and mid tier ‘consumer crap’, it cpuld make a discernable and appreciable difference.
(I think my first rig was a NAD 3020(treble) and Rotel ‘monoblockable’ power amp (bass), later upgraded to two matched rotel monoblockable power amps.
that monoblock switch ruling the waters when cosidering buying ‘more amps’ for only two speakers.
The uplift in sound quality is coming from where?
*less burdened power supplies
*ability to run different speaker cable for different speaker driver and amp pairings
*better lectrical isolation between the channels
etc etc
if your system doesn’t have weaknesses (ie from being the worlds cheapest kit like I was using) then it is hard to imagine the gains to be found.
probably better going down a different pathway
OR
if determined to buy another amp of ‘near identical vintage’; might be great to use them as power amps for a multichannel AV processor/receiver.
My NAD/Rotel setup was wonderful.
for 200$ I had the sweet NAD treble and nuance with the Rotel high damping factor and higher wattage for the more (power) demanding bass drivers.
In fairness the best audio upgrade was some Nordost bi-wireable speaker cable…
I’d seriously reconsider this project, certainly before making my speakers ‘bi-wireable’. (unless that is a personal project and ‘fun’)
might affect resale, and your amps would wear out at a different rate based on one being used lightly and the other being hit harder…
(tweeters are a percent or so of the power/midrange units moght delve around 30% and bass takes the lionshare, being 70%+ of the power needed)
I do confirm at the starting point to hifi budget and sound, using second hand, a match in favour of bi-amping as a pound per sound upgrade might work; but more than likely time and $ spent elsewhere will net seriously more