You are not understanding how a 781-44 (789-44) block works, there is no reason to do what you mentioned.
The 781-44 is a passive device, the power supply plugs in and it supplies power & GND to the +12VDC & GND terminals of the 781-44; and the +12VDC sleeve & GND ring of the TRS connector. You can do the same thing by splicing the power wires into the same wires on the IR receivers, bypassing the block. The IR emitter outputs come from the GND & IR IN connectors of the block, thru biasing resistors.
So what you said you were wanting to do above, is the same thing as connecting directly to the 791-44; but thru an extra resistor on the IR OUT, dropping the IR signal some.

If you take the time to dress your wiring nicely, the IR emitters usually do not look bad on the equipment. This is also 4x better as far as system reliability is concerned, so much can go wrong in trying to IR blast a rack of equipment; I don't have the space to type it all. It's just not a good idea.

I know Xantech says the DL85 is CFL & plasma proof. It is a lie. The DL85 is a great general purpose IR receiver but if you want actual CFL & plasma compatibility, you have to get the DL95 - it is bad ass and works every time.
Note: If the DL85 (or even the DL95) is installed in such a way as to have a light source with a bunch of IR shining right into it... it's not going to work, period. Nothing on Earth will. So make 100% sure that you minimize this by placing the IR receiver in the correct spot. You might even need to build a little shield by wrapping some electrical tape around the IR receiver (with the lip overhanging) to block light from the sides. This will narrow the window of what the IR receiver can pick up.
Note 2: The 490-10 is an old IR receiver that absolutely is not CFL or plasma proof.

It sounds like your whole problem you are trying to get pass, is a very old (or cheap) LCD TV. That is using a CFL backlight. The only solution might be to replace the TV with a more modern LED backlit model, that will not interfere with IR signals.
Again, look at the room and where you have the IR receiver placed. Make sure there are not any CFL lights in the room. Make sure the IR receiver isn't positioned where it can see the front of the TV.

Also, it sounds like you do not want to spend the proper money to make this work. This stuff is NOT cheap, not if it is done correctly.
Using an IR blaster is a lot cheaper than a bunch of IR emitters but it is a BS way to do it. So much can interfere and have problems trying to use a blaster, it just is not a professional way to do things.
All these IR receivers you keep trying to use are either cheap BS (like those Amazon ones) or the lower models from Xantech (which only work in ideal situations). Yes the DL95 is a LOT more expensive. It is so for a reason and maybe what you will need to overcome the interference you are having. This again assumes everything else is good = 1) If the TV is bad and throwing out so much interference as to flood anything you put in the room; sorry, going to have to replace the TV. 2) All other sources of interference have been looked at in the room and made sure you have everything pointed correctly to avoid as much interference as possible.

[edit]: Oh... another elephant in the room of this zoo = Why are you using IR repeaters for a rack of equipment? What control system are you using? The cost of a 'good' IR repeater system is about the same price as the RF base stations of most entry level control systems (URC, RTi, Harmony, etc.) and you get a lot more features & expandability.