Sorry I missed this. For some reason HBT failed to notify me you'd replied.
Gotcha on the Mr Beer. It's actually a pretty neat way to get some batches going!
First, never, EVER use flaked grains in extract/steep brewing. You will gain nothing other than useless sticky glop. Flaked grains must be mashed.
Second, the standard among extract brewers is to use the palest appropriate extract and use specialty grains to arrive at a desired flavor/color. That's not to say you can't use darker extracts. Just be aware that the things which make non-pale extracts non-pale can have a significant effect on how you formulate recipes. When you use pale extract for your base, you can build recipes like an all-grain brewer.
Think of extract like a chicken breast. When you're cooking, you don't want to worry about the chicken breast. You worry about what you're seasoning the chicken with. Same principle applies (generally) with brewing - we use pale malt as our chicken breast. Savvy?
In this case, I suggest swapping the Dark DME for Briess Golden Light. Then add specialty grains to make it a Stout. I'd do this:
2 # Briess Golden Light DME
0.5 # Briess Caramel Malt 60L
0.5 # Simpsons (or other UK) Roasted Barley
The crystal malt will provide a firm body and caramelly sweetness.
Roasted Barley is the signature flavor constituent of Stout, so you need a good wallop of it. In fact, a well-brewed Stout will get much of its bitterness from the Roasted Barley, though hops play an important bittering role as well.
Speaking of which, I'd use 0.5 ounce Galena boiled for 60 minutes. I don't care for late hops in Stout. I find hops flavor/aroma clashes annoyingly with the roasted flavors. Moreover, I find Galena has a relatively coarse flavor/aroma profile.
I've never used the yeast you specify. I prefer to stick with yeasts I've used over and over. In this case, I'd opt for S-04.
May your beer be awesome!
Bob
EDITED TO ADD: Concur on the sugar. Stick with all-malt.
