Yes, they are. You'll be fine with any new hard drive.
Why go Bulldozer? especially the fx4100?
Well their processors only work with their chipsets. bulldozer isn't the best, an older phenom II x4 would be better if they are in-stock around you, otherwise an i3-2100/2120 might be better.
no, intel mobos are crap for anything but just running it. they aren't good for overclocking or anything and really the other brands (gigabyte/msi/asus) are probably better quality too, but with an i3 you can't overclock anyways so that's not a big deal.