image size...what to expect?

I recently purchased a Celestron - NexStar 114 GT from Costco for $198.00
with a $40.00 instant rebate. I felt I got a good deal on this scope. After
the first use...I have to say that I'm disappointed with the size that Mars
appeared. Slightly larger than the eraser on a pencil. I used the standard
10mm eyepiece which gave me 100X. I thought I would be able to see the Polar
Ice caps etc. Is there a better eyepiece that will give me a larger image
with better detail? Honestly, my binoculars and spotting scope were almost
as good as this scope....am I doing something wrong?