I, too, have been using Scottrade for almost three years now. I have been very satisfied. Their fees, regardless of whether it is a limit or a market order, are $7.00. When I have had to call the office, they have been very responsive. I recommended them very highly. I have to admit that the other day they wouldn't take a limit order for stocks listed under $1.00, so you might run into problems there. There was no problem placing a market order for stocks listed under $1.00. The fee is the same regardless of the quantity of any particular stock. I do know for a fact that TDAmeritrade charges $9.99 per trade as I am treasurer of an investment club that I belong to and that is the broker they use. Hope this helps.
Regards, Judy