if you are wanting pounding, loud bass, infinity subs are not the way to go. there is much better for the money. while i enjoy infinity's line of speakers, for the lower range of equipment, their subs are not worth your time.
you would only need two subs if your room is just that big.
bookshelf speakers are fine if that's all your room will allow. 'tower' speakers are great for front/main speakers for their obvious benefit of it being like a built in speaker stand. under all that, the actual speaker components are often almost the same as a bookshelf speaker of the same product line. however, because of the larger cabinet size of floorstanding speakers, you usually get a 'bigger' sound. so basically, if your room allows floorstanding main speakers, get them instead of bookshelf.
bookshelf speakers are generally the standard for surround speakers.
develop a budget and work from there. in the price range it looks like you're going to be working with, Onkyo or Denon would be where i'd look for a receiver.
i would definitely find a local dealer so you can audition the speakers before you purchase.
crutchfield can blow all sorts of smoke up your butt, but they have no idea what is going to be appealing to your ears. also, don't limit yourself to infinity or polk. they make ok stuff, but once you get up to their higher lines that are worth your time, you could've picked up a pair of better speakers for the same or less....ex: B&W
if you have a larger room, skip over the small 'satellite' speakers. they have potential for great sound, but by the time you get a set that would suit a larger room, cabinet speakers with better sound would cost the same.