First off, next time someone has an addictive flash game, keep it to your damn self!
My best so far is 2254. I still can't beat level 5 because I run out of stones. I think the best combo of power ups so far is bouncy stones, extra stone, extra stone, and then extra soldier. More bouncy stones makes the stones too unpredictable in my book. You need the extra guy for level five because you can't take out the second gate before it spits out two guys, and the first gate will spit out one. Then you waste stones trying to crush the men, rather than trying to wreck the castle.