To be honest, what ever you are willing to pay, are the engines worn out, new or some where in between? Hard to give an opinion we would need more information.
The only S2000 I'm familiar with is the Super Tigre S2000.
The Kalt 22 was a predecessor to the Zenoah G23 but was a far cry from having the power of a Zenoah G23.
A DLE 20 will run circles around either of these.
Parts are no longer available for either engine.
Good points! For occasional flights with an experienced user, these engines would be OK. For a new user with limited experience and for someone who wants many trouble free flights, I'd avoid these engines like the plague! Buy new.
If you are sure they are in great shape and need no repairs , each may be worth 100.00 .If you are unsure of their condition they are nearly worthless. Money spent repairing either engine would be better applied to a new DLE 20 or similar new engine.