Upped one is underpowered. We must always take the chance we have no more reverb cards to play. In that case, the unupped one will produce 1 quantum for 0 cost while the upped one 0 for a cost of 3.
You got it backwards, reverb cards become stronger when they are replayed (and extremely weak early game). Atm the upped version is the only reverb card that allows you to replay it without loosing a card draw because of it and pays for itself after 2 uses. So this is a card that permanently buffs all reverb cards every turn while eventually giving more quanta than it costs.
It would seem that reverb cards are supposed to be played in a rainbow ( in "tha Deck"-style with sundials to stop the bleed in early game where reverb cards are next to useless and the upped version is effectively cheaper (QT>any other pillar)). All the reverb cards I've seen are too slow too use in duos and monos effectively, but a rainbow like that can work.
-Soul catcher-syndrome: The card isnt very strong on its own and encourages basing most of your quantabase on a few copies making bad draws likely and PC deadly.
- Niche card: It's either reasonable (or op) in reverb decks or useless in general (This applies to all reverb cards really)
- Upped only: strong snowball effect, cost effectively nothing to increase reverb counter by 1 and gain a lot of quanta (at first I thought the effect cost nothing and was going to suggest to make it scale with 1N only, but this is fine)
- Unupped only: I think its too weak; you really want quanta production to happen early game and cards like nova and immolation are intended for fast decks, which remotely fair reverb decks simply wont be, as these cards are necessarily stronger in late game (besides this card requires an extra turn and can be countered by PC). Increase it to give N+2 (3 on first use) or more. Most of the time its also a really bad topdeck, since lategame you usually have enough quanta (remember all the games you needed any non-pillar card to gain the advantage? I don't it's too many), and it will happen again and again if you use the ability (you can play it and not use the effect to increase reverb counter).
Btw which cards are valid targets for the ability? I suppose permanents and creatures on either side of the board are a no-brainer, but what about other cards and cards in your hand (or by extension your opponents hand
P.S.: A series where cards become stronger the more of its kind are left in the deck could be interesting too.