Well, I have never had any issues with Day Trading options. Did a trade last Friday morning, and later in the afternoon I saw that my "Option Buying Power" was same as my account balance again. Spreads may be different though.
I personally use TOS as well. I got setup at $4.95/ticket and $0.65/contract. Since I usually only trade between 3 and 10 contracts per leg/trade, this has worked out better for me. If the OP is making 25 contract trades in a single leg/trade then one of the flat ticket rates would probably be better for him IMO.
You may also want to check out eoption.com Next to optionshouse, they would be the cheapest for 25 contracts. Also, great customer service (I have been recently researching brokers and have had nice interactions with them). So, they suit my needs (and was the best price i could find for multiple lots). E