Warning, slight detour ahead......

I've been following this thread and others, and learning a LOT. I've got near-zero knowledge of the DSLR world, but am itching to upgrade from my 6mp Canon Powershot. Prior to going digital I used a Canon EOS A2 for about ten years and loved system and the substantial size and weight. I only had two Sigma lenses for it, a 70-300 and a 28-105 Aspherical.

My Canon's AF died, and the body is worth pennies on the dollar now, so with some sadness I'm moving on. I'm amazed with the image detail of DSLRs, and I also know that high quality lenses play a huge part in the quality of the image. My question is, are my Sigma lenses compatible with the Canon DSLRs, and if so, am I kidding myself with their quality for that application? I can walk away from them too and start from scratch if need be.

I'd like to stay with the same body and lenses I start with, rather than play the upgrade game. Currently I'm leaning towards a 5D body, and a pair or trio of L lenses as I can afford them. I'll admit to being a little scared at the prices vs. the rapidly advancing technology and changing market. I knew my film SLR setup wasn't top of the line, but I'd never have guessed that it would be extinct in only ten years.

Is the used market a wise place to shop for lenses, or do the high-end lenses get so much use that by the time they're for sale the AF or IS systems are mostly used up? Same situation with the pro and semi-pro used bodies? It doesn't seem like good photo gear depreciates as rapidly as snowmachines, and so maybe I'd be ahead to buy new. I'm very easy on my gear, but maybe most photographers are too.

Thanks in advance.

Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery.
--Winston Churchill