Here are my personal opinions.
1.If you have any processor is better than E21x0, it is no way to dump it and get E21x0 especially in E4xxx case.
2.If you want to wait the next big upgrade while you are able to keep things going. The e21x0 is the way to do.
3.It is different between you need a processor with more cache vs. you feel comfortable that you own a processor with more cache. Always go for the comfortable level because you donâ€™t want to regret later.
4.With in E21x0, E2140 is definitely a good start point. Between E2160 and E2180, they have same scale. Most E2160 in current market is L2 and E2180 is M0 which 62c vs. 71c. As far as it comes to OC, you can tell difference if you apply a 60% or 70% rule.
Others feel free to comment.