Quad ESL Cap mods

Mundorf has a 220uf MCap, not the tube line.

Where is this in the circuit? I highly doubt a cap that large would be located anywhere near your tweeter circuit.

You can solder a few smaller values in parallel. Since you're looking to upgrade, I would avoid electrolytic caps entirely. Dayton, Solen, and Mundorf all have large values.

This is a input cap -- right after the binding post along with a resistor.

I believe it is a coupling cap, acting as a high-pass filter (filters out the deep bass), therefore it is very important for sound quality.
220uF in film caps will be very costly and occupy a lot of space, about the size of four soda cans. The least expensive option is four Solen 47 uF / 400 Volts caps plus one Solen 20-30uF uF / 400 Volts plus one Mundorf Silver/Oil 4.7 uF, all in paralell.
Since the original electrolytic cap has a tolerance range of +/- 10%, this combo will be in the ballpark.
You may want to do the full combo with Mundorf Supreme caps and use a 4.7 uF Mundorf Silver / Oil as a high frequency bypass cap.
There are many cap comparisons on the net, most agree that Mundorf Silver /Oil is one of the best caps regarding clean and extended treble.
I have experimented Mundorf S/O as compared to Kimber, Auricap, Hovland and Jantzsen film caps in the tweeter network of my dynamic speakers, all those caps sound good but Mundorf is ahead of the pack IME.
I hope this helps

I have a 220uf Mundorf here and it's only the size of 1 soda can.