You are correct. There is no doubt that many of these things can be achieved for a fraction of the cost and effort in software! For chords you are almost certainly better off with a computer and a synth that can respond to polyphonic midi.
My personal take on it is that I find software less immediate and I usually work all day on a computer so for me it is worth paying the price of entry into modular to get away from it to make music.
Obviously this is a personal decision that only you can make :)
I would say 2k is a good starter system, either off the shelf or build yourself (I don't mean DIY).
If you are interested in modular, I think rather than trying to go for this specific musical idea, you are probably better off choosing a system (Erica, Make Noise, ALM, Endorphin.es - depending on your musical style preference) for your 2k, knowing you are getting a complete very well thought out system that will give years of enjoyment and exploration, give that a go for a while, learn what the strengths of modular are and then see what else you would like to do.
Whatever you decide I wish you good luck!!