Help....I have a blank slate and am flying blind

I am not an audiophile and am trying to get my arms around the whole thing - quickly. The water is deep. I've never had a nice system and am buying a new house. At the expense of all furniture, I want to rig the place for sound to the chagrin of my wife (who hopefully will not discover this post) and 4 kids (though the kids may well opt for music over furniture):

I basically want the system to be PC driven, but also have a couple of components that I would like to include (Teac H500 CD recorder/player and XM receiver). I have at least 4 rooms to rig and am shooting for low to mid-level audiophile grade.

I am thinking of setting the system up something like this: (but am missing a few pieces, which is where I need guidance):

750 GB external hard drive (just purchase new) --> P4 laptop computer (just puchased used) --> DAC (perhaps HAGUSB and/or something else --> cheap/decent receiver (need to purchase or perhaps a pre-amp with A and B channels):

A channel (for room 1) --> good amp (need to purchase - perhaps simaudio i-3) --> totem hawk speakers (just puchased);

B channel (for 3 other rooms) --> cheap amp (need to purchase) --> russound 10 speaker selector (just purchased) --> 8 inferior speakers in 3 different rooms (have them);

The critical threshold at this point is PC to receiver or pre-amp. I use iTunes and have a ton of music in Apple Lossless format, so compatability is an issue I think. My sense is to avoid a wireless connection and soundcards (I've heard they are inferior), so I think I need some sort of DAC, which is where I get off the bus.

I was looking at a HAGUSB (Hagerman Technologies - under $100.00) and a squeezebox ($299 model). The thing I don't like about the squeezebox is it appears that I would have to control it through their box and not through the PC/iTunes. If possible, I'd like to simply use the laptop as the the control center with iTunes as the interface (if that is the right word). I'd rather not spend more than a few hundred dollars on a DAC (I still have to purchase two amps, a receiver or pre-amp, wire, connectors, protectors, rack, etc.)

The second (less critical) threshold is choice between a receiver and a pre-amp. I suppose I could buy a cheap but decent receiver with an A/B channel, but I don't think I want the music filtered through a receiver. Is there a pre-amp with an A/B selector that I could raise the roof by selecting both A and B? This may affect the DAC connection decision from the PC. I have a couple of other components I want to include (CD player and XM receiver) so maybe I have no choice but a receiver - maybe I just answered my own question. You can see I am processing.

Long way to the short question: What is the best way to get from the PC (via usb?) to a receiver or pre-amp in a way that is both compatible with iTunes and would be considered "acceptable" from an audiophile standpoint at a reasonable cost (under $400.00)?

Any assistance is appreciated. Please respond in crayon and do not use "big" words.