I'm going to start commuting to work. I'm about 7 miles each way. I don't want to cary a backpack, so I'm looking into to racks and panniers. I need some advice on how much space I really need. Here's what I need to carry with me:

- 15" Macbook Pro laptop
- Charger (could leave at home... I have two)
- a few papers/journal
- A change of clothes (I typically wear shorts, t-shirt, underwear, socks, and tennis shoes to work).
- Gym towel
- Shampoo, body wash, deodorant, comb
- gym lock
- Lunch/snacks
- iPhone

In addition (could go in same bag or separate), all the bike stuff.

- multitool
- small first aid kit
- two spare tubes
- to CO2 cartrdges
- tube changing tool
- broken chain thing (link)
- lights
- etc

I was digging the the Ortlieb Commuter bad 3.1, but wasn't sure it that would be large enough alone. My shoes will take up the most space. I'm also looking at the Ortlieb Downtown 3.1. That's bigger and has a laptop sleeve. Does anyone have any experience with either of these bags? Are either big enough?

Of course, I could get a back roller.... but they are really big. They would do the trick and would provide for grocery store runes as well... but not sure if I want something that big for a daily commute.

Thoughts?

I also really dig the 3.1 system. Is there anything better that I should be looking at?