Airport Extreme or Express

not sure exactly what Im wanting here, maybe Im wanting/needing both? Here is what Im trying to do.

I currently have 3 PCs (will eventually be replaced with mac minis) in my house and my Macbook. I have ATT modem and a wireless router (not 802N). My PS3 and main PC are hooked directly into the router. I then have the other 2 PCs and Macbook connecting via wirelessly.

Here is what Im wanting and not really sure how to achieve it. Thinking extreme or express is the right direction..

1. Like to play my itunes through my living room stereo system (but router, etc not in living room).

2. Like to share a printer throughout at least one PC and my Macbook. If I can print with all PCs thats even better.

3. I have 2 external hard drives. One is a 320gb smart drive USB that I currently use for moving files around from home/work, etc.. I also use it as a backup for all my important stuff like photos, videos, music, etc.

My other is an old PC hard drive I took out of a computer. Its not huge, at only 100gb. I ordered a hard drive enclosure that is ethernet capable. Should be in anyday now. Not sure what my plan is, but hoping one of these to be my timemachine backup and other to be able to access when away from home over the internet with an IP address or something?

4. like to be able to network all my computers together. Not sure how or what to do here, but like to be able to access files from PC to Mac and back and forth..

any ideas on where I should go for all of this? Thanks!

Sounds like you need both A. express to send tunes to HI-FI thats what I do
and A. extreme so I can run Time Machine off the usb then an ethernet
all in one printer and an ethernet hard drive for sharing and extra storage and that leaves me one extra port for routing to a switch to go to the rest of the
house for hard wire if I need it.

I have similar needs and found that having both works great. The extreme is upstairs in the 3rd bedroom with my desktop, scanner, printer, media server, etc... and the extreme is in my living room working with the stereo, laptops and Apple TV. The bridge created by using the Express to extend the network is nice as I get better signal and can get online in the basement and garage now as well.

so let me know if I get this straight...

I get an extreme (basically just a router right?) and I hook up my usb external hard drive to it and it will allow me to access this HD from all the computers connected to my wireless network (and ones hard wired too it). This will also allow me to share a single printer throughout the network as well.

Then get the express for the itunes to my stereo.

now only 2 questions Im still foggy on. My other hard drive that is ethernet capable, will I plug this into my extreme or just my macbook? If into the extreme, do I do it with ethernet cable? Will I be able to access this ethernet HD or my usb HD when away from home? Like if Im at work or in a hotel, will I be able to get files off of one of my HDs?

oh and one more thing. which HD should I setup for time machine? And if I use time machine on one of my HDs, will I still be able to use it for putting files on it also? Or will it only be a "time machine" HD now?

okay, let me sum it up for those who do not want to read an entire book up there.. 2 questions left.

1. if i get airport extrme and hook up a USB external drive to it, i can access it from all the computers on my wireless network. BUT.. can I access it when away from home with an IP address or some other way?

2. if I use one of my external hard drives for time machine, can I still use that hard drive for storage for personal files as well? Or is it a dedicated time machine HD?

1) Yes on the wireless network part. Away from home you will need to set up some sort of VPN tunnel - I know nothing about how to do that.
2) Yes, a time machine drive can be mounted by multiple computers and used as a time machine for all of them. It can also be used well as a plain old external/networked HDD to save files to. I have a 750GB I use for Time Machine for 4 Macs and also save installer .dmg files in another folder on it.