HTC Touch Diamon 2 and Mobile Internet

Okidoki. Going to get myself a new phone today. I need it for business, so outlook sync, word, excell etc. It needs to have decent internet conection whilst on the move as well. Sofar the best contender is the HTC Touch Diamon 2. However with the contract that I would be getting myself into, I would only be getting 250MB a month. Do you think thats enough? Im not watching vids or downloading big files, just selling stuff on ebay and the likes. Cheers in advanced!
Max