upgrading Cort Action Bass

Two answers to your question. First, if you upgrade, you are not increasing the value of the bass that much. I probably have over $400 invested in my bass, but I doubt I could sell it for more than $200. The parts individually are worth more than the bass.

The other answer is, yes, it's worth it. THese basses can sound really great with upgrades, but you still have to be careful. there is not much room for a battery, so would have a hard time in upgrading to making it active.
It just depends on how much you want to spend. Drop $150 on new pickups, and you have a bass that will sound a lot better than the total of its parts. Since you already own it, and you live in an area that might make it difficult to get some of the bargain that you see in the USA (like the lakland skyline series), I say go for the upgrade.
Here is a link with a recent talk about upgrading an action bass