I don't know about z2300 or vs4121, but I own a c3 and would definitely NOT recommend it.
It's extremely underpowered, which results in hugely underwhelming bass.
I put it up for sale last month but am not able to get rid of it. Everyone who auditioned asked, "iska woofer nahi chal raha kya?" No one can believe an 8" sub can give such poor output.