Recently got 60 pounds of Caribsea Sunset gold sand for my 40B. This would make my substrate depth 1.5 inches deep. Would this be enough for a planted tank? Or should I get an extra bag and get it up to 2 inches?

Grab an extra bag... I went light on a 65 gallon a while back and hated trying to get plants established, probably 1.5" depth or close to it. Once rooted it was fine... but it looked kind of funny with the sub barely being visible above the bottom bracing, and replanting the same grouping of plants 15 times before they took root created full sentences of profanity.

So did you actually have plant issues or was it only an appearance thing?

No plant heaalth issues per say, just a hard time planting them and getting them to stay put.

Visuals weren't the greatest either.

3 bags of eco-comp on a 36" x 24" footprint.

Well the visual part I could definitely understand on a 24 inch tank. On a 40B it wouldnt be too bad I would assume.