didnt probe.. coz still at work didnt engage on phone too long...
Probe more. Also, read more before you spend 2.5k$ easily for something where you a) are not really sure what it is (USM, IS, constant aperture) and therefore b) don't know if you need it. I suggest you get the 40D and the Tamron 17-50 f/2.8. That's a reasonable set and you can learn from it whether you need IS, USM and all the other stuff or not.
I have the Tamron 17-50 and I notice the noise during focusing but it doesn't bug me at all. It only occurs sometimes in low light / low contrast conditions. If I know the situation cannot even take this little noise I'll use manual focusing and the focus confirmation.
Filter or not - there are many discussions and opinions. Basically it's an insurance: you buy it to prevent something more expensive happening. It's rather a personal preference than a photo-technical issue here. But it can become an issue (vignetting due to filter stacking).
Get two CF cards instead of only one. It's better to have a backup card and not putting all pictures on one. The Canon standard bag will be enough for this setup.
Regarding drybox ... I saw one offer in Buy & Sell here, 30L. That's enough for a start and will even be sufficient for the next 2 lenses. Nothing wrong with getting 2nd hand, they usually come with 5yrs local warranty and the reports here about repair cases sound good (fast and good response).
Go and enjoy taking pictures before you gear up with more equipment. Buy only what you really need and you what you cannot overcome by other means. A tripod is more useful for night shoots than any lens (and also cheaper).