'Bad' is subjective term. It is certainly outdated, much cheaper 8100 can achieve same performance as 7500. But that does not mean it suddenly has less performance because of that. If you were to buy it today, that would be bad deal, but if you have it it is still solid 4-core performer. It may get a little short in uses that need more that 4 cores (streaming during gaming for example) but mostly its fine.
Now, for the upgrade: without changing motherboard, the only sensible upgrade is 7700(K), but I don't consider it worthy for now, unless you can get way below MSRP.