Sharing data on PC network

I haven't actually switched, yet, but would really like to. I've owned every iPhone model ever made, as well as the iPad 2 and now have iPad {3} on order. I'm now seriously contemplating a 27" iMac. What makes this especially interesting is that I've been a Windows programmer for 25 years and used to be very... ummm... errr... "anti-Apple". However, I love my devices and how they just work, and I've been playing around a bit with iMacs and MacbookPros and they just seem to work so simply and elegantly that I have to have one! I'm taking a lot of abuse from co-workers over my iMac interest, but I'm pretty much sold, regardless.

I'm in the process of making sure I'll be able to do everything I need to with an iMac, though, and that I won't have any regrets. The biggest concern is my home network of multiple PC's and 12gb file server. They won't get switched over anytime soon.
So here are my questions:
1) Will an iMac be "smart enough" to just tap into that network, see all the shares, and be able to access remote files?
2) Will it be able to share files on it's own local drives with PC's on the network?
3) I believe Macs, by default, install applications to the "Applications" folder. What do they use as the default location for user settings/documents?
4) Is it possible to change the user folder, to put it on a second drive? I saw this question asked elseware and every answer said that would be stupid to do. However, I would go with a SSD system drive, and I don't want all my documents, photos, music, etc. to all end up on that (small) drive. I would want them all on a separate "data" drive. I don't think that is stupid, as it works spectacularly in the PC world.
... two more questions:
5) Can I connect my Logitech Z-5500 5.1 surround speakers to an iMac? I noticed that I do have an optical input for my speakers. Is there such a thing as an optical cable where one end would go in the mini-plug jack on the iMac?
6) If I absolutely have to run Windows for some legacy applications, whether it be in Parallels, VM Fusion, or via bootcamp, will the iMac recognize all the USB ports and see devices connected to them? This may seem like a stupid question, but in the Windows virtual scenario, it's a major problem... no or limited access to external hardware.

Thanks for any assistance. I apologize if these were all answered somewhere else. I did do a bunch of searching around, but didn't find any definite answers. I'm looking forward to joining the "club".

I will try to answer these questions as best I can as I was in a similar situation after switching about a year ago.

1: The iMac will definitely be able to "see" all your Windows shares as it is fully capable of recognizing and connecting to SMB shares. As long as you have your permissions correct there will be no issues there

2: Yes, OS X can create SMB shares from itself so your Windows PCs (and server) should be able to see and connect to them. Again, permissions.

3: Yes, Applications get installed to the "Applications" folder. User files go into the appropriate user's Home folder. OS X uses a Unix-type directory structure, so if you've ever worked with Unix or Linux you will be familiar with it.

4: I don't know about changing where the actual Users folder lies on a physical filesystem, however I have all my data stored on an external drive with no issues.

5: I don't have any experience with that so someone else will have to chime in

6: Whichever option you choose (I've used them all) I've never had any issues with recognizing external devices as long as the ports/devices are passed through to the VM properly. In BootCamp you install Windows drivers (which are provided by Apple) for all the hardware in your Mac so there should be no issues there either.

Hope this answered most of your questions.

Yup. That answers lots. Thanks a lot.