Bicycle Mechanics - Thinking about a new stem

I ride a Gary Fisher Kaitai and it suits me just fine (until I'm readin for a roadie in year or so).
I've gotten a lot pleasure from this bike but for one thing... I feel that -while everything else feels fine- I have to lean forward or reach for the bars more than I'd like. It's pretty hard for me to keep my elbows bent.
The bike came with a 90mm, 10 degree stem and I'm thinking that replacing that might help.
But do I want to go shorter? Higher? Both? What effective difference is made when switching to a 60mm 10 degree or a 60mm, 25 degree or a 90mm, 10 degree or whatever. Seems like a simple, cheap, effective change? Thoughts?

I ride a Gary Fisher Kaitai and it suits me just fine (until I'm readin for a roadie in year or so).
I've gotten a lot pleasure from this bike but for one thing... I feel that -while everything else feels fine- I have to lean forward or reach for the bars more than I'd like. It's pretty hard for me to keep my elbows bent.
The bike came with a 90mm, 10 degree stem and I'm thinking that replacing that might help.
But do I want to go shorter? Higher? Both? What effective difference is made when switching to a 60mm 10 degree or a 60mm, 25 degree or a 90mm, 10 degree or whatever. Seems like a simple, cheap, effective change? Thoughts?

See: http://sheldonbrown.com/handsup

Nobody can give you a numerical answer that is meaningful, any more than someone on the internet could tell you what size shoes to buy.

Sheldon "Hands Up" Brown

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A shorter and higher stem would be a good place to start. How short and how high? Well, unfortunately, unlike clothing stores, bike shops don't have fitting rooms.

So you have two options: 1.) talk to someone at your LBS and let them know what you want to do. Buy a couple of stems (they'll love that) and experiment. 2.) Get a bike fitting. This was you pay your money, get to experiment, and leave the shop with a stem that fits your riding style.

Understood, gentlemen. I certainly not expected nor asking for absolutes but more for some basic ballpark idea of the "problem". One question (vaguely implied but) not addressed is what impact would these dimension changes have on handling, responsiveness, and/or stability?

Goodness, I almost forgot to say "Thank you"
So... Thank you!

I'm sure i'm repeating much of what Sheldon's linked to... but i'll forge ahead anyway.

In my experience, stem adjustments of 10mm are barely noticeable in regards to comfort. Even moderate changes in stem length--about 20mm to 30mm-- will have little noticeable effect on your bike's handling characteristics. I'm sure that an engineer would differ. In a nut shell, a shorter stem will make steering less responsive and a longer stem will make steering more responsive.

That said: For your comfort, I'd suggest that you start with a higher position for your handlebar. (Just change one thing at a time!) So that means look at a stem with a higher rise.

Here's something to know about the extension vs. reach of a stem. For a given extension, the reach will change with the rise.

For example:

A 100mm extension with a 6-deg rise will have a reach of right about 100mm.

A 100mm extension with a 40-deg rise will have a reach of about 90mm (maybe a bit less).

You'd have to sketch this all out on graph paper with a protractor to get the exact numbers, but this should give you an idea of what happens to reach as angle changes.

I'd suggest that you take you bike to your LBS and ask for a couple of stems. Ask if they wouldn't mind if you held one up next to your current stem. That'll give you an idea of where the stem will put the handlebar.

Good luck!

P.S. As for the amount of money you'll spend? Look at it this way-- it's an investment. Your comfort is important to your longevity in this sport. Personally, I plan on riding my bike until the day i die. So spending extra to ensure my comfort is okay. I'm not quite sure what to do with my collection of saddles and stems...