There's a difference between 'classic' smooth bubbly acid and dancey
distorted acid. It's true many analog synths can do distorted basslines
but I only know 3 clones that sound like a real 303:
Analogue Solutions Trans-Bass-Xpress Bassline TB-X TB-303
Adafruit x0xb0x
AudioRealism BassLine 2 (soft synth)

My friend has a real 303 and after many tests with other clones/synths
(basstation, mc202, syntechno teebee, freebass, rebirth, etc) and if
you need a 303 I would recommend a xoxbox, they are bang on.

I am yet to hear the doepfer 303 filter in action, if anyone has any
audio samples I'd like to hear them.

John.