I've got one of the professional series Kitchen Aids (and my parents have the traditional version to compare and contrast). If money isn't a huge deal, then getting the professional series comes with a more powerful motor and a heavier base that will stop the mixer from "walking" around the counter if you put dough or something dense in the mixer.
One odd thing that I didn't expect is that the mixer is really inconvenient for small things. It can whip up like a triple batch of whipped potatoes, but it has the darnest time whipping up a little bit of whip cream or a little merangue.
Kitchen Aide's attachments are pretty rock solid... One of our more "fun" attachments that we have is the ice cream bowl. Freeze the bowl, dump the ingredients and set the paddle on low. Again, with the professional model, the motor is strong enough to churn a bit longer than traditional other ice cream churns...
IMO, if you're a big dough cook, go w/ the stronger model, otherwise the smaller models should be great.
EDIT
In an interesting note, my sister has one of the smaller models and it did infact "walk" off the counter a few weeks ago... The whole machine went crashing to the ground... She picked it up, dusted it off, but the only damage was a small piece of plastic broke off... Gotta give it to Kitchen Aide
The only one that could feasibly handle it would be the grinder. However, in the manual http://www.kitchenaid.com/assets/pdfs/product/ZUSECARE/FGA_Use%20and%20Care_EN.pdf on page 5 it states "Note: Very hard, dense foods such as totally dried homemade bread should not be ground in the Food Grinder. Homemade bread should be ground fresh and then oven or air-dried." If dried, dense bread is too much for the grinder then peanuts would definitely be to much as well. My recommendation is to use a food processor.
Best Answer
For some brands of stand mixer, the paddle attachment is the sort of default attachment for basic mixing, and for creaming. It does not excel at whipping egg whites, or stiff bread doughs, but these brands come with a separate whisk attachment for that purpose.
Of the two sets of beaters pictured in the image you have shared, the ones in the machine are your standard beaters. You would use them for almost every task--they are general purpose, although perhaps not ideal for everything. This includes mixing, creaming, and whipping egg whites or whipped cream.
The kind of corkscrew shaped ones are intended for kneading stiffer bread doughs.