Hard to say, because the devices (the preamps) may vary.
I can’t give you any advice on which one will do the best job - maybe someone else.
You’ll need one with pre out connections.
If you have one with line outs, they normally will output at a fixed level. These are made to connect to an amplifier. This might work with the A9’s....but in that case you’d have to control the volume there - on both A9’s simultaniously (which in real life will not be possible).
There are some just stereo, however most people use a multichannel receiver with preout connections.
You will have to deal with the question of how to control the volume as well.
Most tv’s nowadays only have digital outputs (most seen are the optical outs).
The problem there is that these are fixed/at a fixed output - means you can not use the volume control of the tv.
(Some people alternatively use the headphone output - these in general are of lower quality. I would not recomment that).
With a preamp you will be able to control the volume output from that device - some preamps have a remote control, the multi channel receivers certainly have.
In that case you would have to leave the volume controls of your two A9’s untouched........after you have level matched them to each other.
Also consider, that if you place the two A9’s (as L and R) relatively far from another, it will be hard to sit in the sweetspot - that is where the phantom center is created.
Without a dedicated center channel (for watching tv, movies, games) and only with a stereo setup, the phantom center tends to move away from the place where the screen is, when you move.......and spoken words will be less audible.
Not saying that you should not do what you have planned - just saying, that it might not be as easy as expected.
MM
