Which of the following do you think I guess get next for my cello?

1) A set of strings (yet to be decided, but this is for later, perhaps a few months, as backup strings)
2) A carbon fibre bow (90 USD?)
3) A carbon fibre endpin (50 USD?)

Which one of those will most improve my sound? I have an intermediate wooden cello bow, and I am thinking of using a carbon fibre bow as my main bow.
or will a carbon fibre endpin help my cello more?
Honestly I'm not too keen on the strings, until later, so it's either a bow or an endpin.
or you can suggest alternatives, but I can't think of anything else. I just want my cello to sound warmer and more mellow. My cello is REALLY harsh on the high notes (from middle A onwards it gets unbearable, I'm thinking of getting a soundpost adjustment too.). Advice and comments are welcome

As for the strings, I am looking for a student priced set of strings which will give me a really really warm and mellow sound.
Jargar A
Jargar D
Pirastro Chromcor Plus G
Pirastro Chromcor Plus C

Not sure of the above combination will work, but it's the cheapest and I have had most experience with them (besides the Jargar D).

Well, what strings do you use at the moment?
What type of cello do you have? (nationality...age...?)

I really don't think it's worthwhile looking for the cheapest combination of strings. All that's likely to do is reinforce the bright, harsh sound you're trying to get rid of.

Is there a luthiers nearby where you can actually try strings on the cello without buying? Strings are different on each cello.
BUT! For my money, these are the strings I like playing on:
Larson, or Larson soloist A and D - I know a few people who say that normal Larson are slightly more mellow than the soloist type, although they don't have the projection. Soloist Larson are obviously a little more expensive.
For G and C, I swear by Spirocore. These are gut core, and, for my money, give you the most lovely, round, rich sound. They take a little playing in - they sound metallic at first - but they develop wonderfully, and since I first used them, I haven't stopped! Also, they last longer than normal strings (but they are a little more expensive).

For my money, I don't know your cello, but if you have a set of cheap strings on it at the moment, I really would invest in a new set - especially at the standard you are. I don't know how much difference a new endpin will make. But strings are incredibly important and could transform a cello.

As for the bow, can you borrow anyone's good bow and have a go on it to see the difference it would make? (Again, please don't get a carbonfibre bow only because it's cheap! MAKE SURE YOU TRY IT FIRST - incredibly important! Some carbonfibre bows are excellent - others would be better in the scrapheap...)