To be honest, for me i went from a Nikon D70 to a Canon 5D with 24-70L and didn't see any difference in my photos, it certainly made the photos sharper, etc but that was it, it didn't make me a better photographer.
My option though, for me i still look for images in the same way no matter what the camera.
Did exactly the same, but with the 24-105L....
I also have a 400D as light weight travel camera. I replaced the original 18-55 lens with a Sigma 18-85, which is much more useful and sharper, so I'd suggest a better lens first.
Re... RAW.... For me it avoids JPEG compression, avoids camera processing, I prefer to do it in software on the PC, so I can apply what I want to each picture.
I have the Canon to set to RAW+JPEG-M... So I have medium JPEG file as quick reference and review before working on the RAW file...
Those who advocate shooting manual as some better form of photography... I assume you use a handle held meter ?? If not why you wasting your time ?
If not you have no more control than other modes.... and some one using Exposure Compensation dial in AV or TV mode.... I use Exp Comp a huge amount... and Auto Bracketing is very handy.
I also like the grid display switch on in the view finder, if it's available. Recently bought a new focus screen for my Contax, to get the grid, which has thirds marked..... They thoughtfully put the autofocus points at the thirds intersection points...