In reply to your concern with upgrading your cpu, I think that since you have an i3 model, upgrading to a i5/i7 shouldn't be a problem, as long as you have the same socket number of cpu.
If you post a question to your motherboard manufacturer regarding this issue, they would confirm this is possible or not.
You may need to upgrade your heatsink/fan unit for dealing with the extra power of the upgrade.
My i5 is a 4th generation model although Speccy lists it as 6th generation, so check your cpu's details from the model number with Intel.
Lastly, do you really need an upgrade, remember that the cpu's are manufactured the same way with relation to their generation and so each of the i3, i5, i7 etc are chosen by the testing processes after manufacture.