My first post is a seat post post

I'd suggest continuing to put the miles on what you've got for now. I finding that the more riding I do, the more my purchases/upgrades pick themselves based on the problems I want to solve, aches/pains, weaknesses in handling etc.

For what it's worth, a good set of tyres will help you achieve greater comfort, ride, speed and reduce weight a little. SammyG's suggestion of light latex tubes would reduce the weight even further, but you'll forever be pumping up your tyres.

You don't say what type of riding you do, but I suspect a set of Continental Gatorskins or GP4000s would make the world of difference to the feel of your bike.

That's a decent seat post, I have one, its a little lighter, and does take some of the road buzz out of your bum

Here is my bike:
http://samuelgray1987.tumblr.com/

If you wanna be a weight weenie go and buy some kitchen scales, take your seatpost out, saddle off, weigh each individually, check the weight of your stem. How much do your tires weigh? How much do your inner tubes weigh?

I reckon light tires and very light latex inner tubes, perhaps would come in at 500g which may shave 300g off your bike and reduce rolling resistance.

Yep wheels are without doubt the single best place to spend your money. Reducing rotating weight will make loads more difference than reducing the weight of your seatpost and decent wheels will dramatically improve ride and handling compared to the bog standard wheels that come on most bikes.

Dont know about that seatpost but my first port of call for an upgrade would be wheels if I were you.