What are you daytrading, for starters? Sounds like stocks.
So if you're moving large share blocks of stock you should look at per-share pricing from firms specializing in daytrading. Doing it through E-Trade or Schwab likely won't give you the execution speed or pricing you need to succeed and as you said, the commish will kill you.
If you're moving futures, look at dedicated futures brokers -- you should get $3 or less round-trip per contract.