When I started out I had a 50D and all bar one of my lens purchases where based on a FF upgrade.

It's funny you mentioned the 24-105 as I found it underwhelming on the 50D but as soon as I strapped it on the 5DMKII it came into it own. Love the shots it produces.

IMHO you cant go past the 50 1.4. I love it as a all rounder prime. I was at family friends wedding the other night and it was nearing total darkness inside the reception venue. Got some great shots at 1.4 ISO 3200 as I need to keep the shutter speed up due to bad hand shake.

The 70-200 F4's been on my mind for a while now but some of the shots from the 70-300 IS stop me. I've been leaning towards the 200L 2.8 II of late as a friend has one and it's a great lens.