Cs200 on your heat exchanger, that has 9.5kw @ -20c, more than powerful enough to keep up.
Unistat 815 on solvent tank to keep sub -60c.
The 815 could also keep your columns cold, but then you might be extending the range the fluid has to go and it might not keep up.
I have an 18kw heater (you’ll need three phase) which is very inexpensive at around 6k.