bc -
You might spend some time thinking about where you want your power and how much you want to spend. 26s always seems to work well, and there are a number of others -- like the Andrews 37 and 44, Woods tw6, S&S 510 and more that many members have used in builds with good results.
A search might help you figure out exactly what kind of power you're really looking for and give you an idea of your options and cost. You'll want to consider head work too and doing it all at once is the most cost-efficient way to go.