I'm considering replacing my passive preamp with a tubes. Is it worth it?

The answer is "maybe". Some will tell you "yes", some will tell you "no".
Since it's your money, the only opinion that really matters is your own.

So you should just look for a tube preamp on the used market that is a good deal and try it yourself. If it works, great. It it doesn't work out, sell it, and go back to the passive. At least then you will know for yourself.

I totally agree with jmcgrogan2 it depends but I see some pretty cool tubed preamps for sale here in your price range.

https://www.audiogon.com/listings/tube-blue-circle-audio-bc21-1-tube-preamplifier-upgraded-9911-2017...

https://www.audiogon.com/listings/tube-lector-zoe-tube-preamp-2017-02-12-preamplifiers-40059-prospec...

No affiliation with any sellers those both look like good deals and good preamps, good luck and happy listening!

What would I expect to be different with the tube preamp?

The opinions are appreciated so thanks