Well, there's not much that will do everything for you, honestly, and the good stuff actually doesn't force you to use a single interface... mail.app has it's problems, but most people agree that GTD would say keep your mail in your mail application, it's better sorted that way anyways... and iCal may have some replacements, but not too many are hands down the one to use.

I suggest you check out Kinkless's kGTD.

Hope this helps,
-Allen

ps- for really easy input of various things into a simple text document (which can then be used later on during a review of tasks etc), check out Quicksilver's append and prepend text. Merlin talks about this on 43f a bit. I've just now used it for the first time- couldn't have worked easier for inputting simple things into a text app. BTW, when you have kinkless' kGTD and Quicksilver installed, you can also use a script to put tasks into your inbox straight from Quicksilver's popups.

First, take a look here: http://groups.google.com/group/macintosh_pims?lnk=li
Second, don't waste your money on StickyBrain or anything by Chronos.
Third, I here you; mny of us are in search of what you want and have found some options (see "First" above)
Here is a short list that works with iCal to some degree:
Circus Ponies NoteBook (this could serve both your Catalog and Project needs)
Process by Jumsoft
OD4Contact
CRM4Mac
XTime Project ($100)

There are a slew of choices (again see "First" above). Both OD4 and CRM4 are on the verge of a major update. Though I don't like it in it's current state, some folks like Life Balance by www.llamagraphics.com ; it too is due for an upgrade but no telling when as they spread themselves way too thin, supporting Mac, Windows, Palm and now Windows Mobile, going for more instead of better (IMHO).