SoundOnSound *is* good, but the quality of their review writeups can be a bit variable. For 8-preamp Firewire interfaces, for example, you find plenty about how it connects to the PC and everything, but generally there's bugger all mention of whether the preamps are any damn good, which I'd think was something they should report. There's often some *very* good technical articles in there though.
how you use either a digital or analogue mixer to get the signals into some sort of software
You don't necessarily need to. The easiest way is that one mic goes to one input on your interface box. Record like that, then you can juggle things around afterwards however you want on the PC. If you record via a mixer, generally you'll have more inputs than there are mixer outputs, so some things end up mixed together. This might be OK if you get the mix just right, or if you're only recording one input at once so you've got enough outputs. But if you want to record a whole band playing at once, and you need to mix several inputs to a bus, and you can only record the bus and not the individual instruments, then you can't retrieve the situation later. You can't unscramble the egg, in other words!
Digital mixers have the big bonus that they *are* the interface box! So you can put all your inputs into the digital mixer and get a true multitrack recording of everything. My Behringer DDX3216 for example does just this, sending all 16 raw input channels out over fibre-optic cables to the PC. When I can afford it, I'll likely upgrade to a Tascam or Yamaha, because the Behringer's mic preamps aren't very good and the FX can be a bit iffy too. But I need some better mics and some outboard gear before it's worth upgrading that.
Basically you usually get what you pay for, and whilst Behringer might not be brilliant, they often do the job for a lot of people who want to record reasonable quality demos or live recordings. Once you start looking at Neumann mics and stuff in that sort of range, of course, then Behringer is probably a no-no. :-) But your sound is only as good as the weakest link in the chain.