$1500 - $1800 Server for Database and Filesharing

File serving usually does not put much load on the CPU's but you will want a 1 gigabit network on it (pretty much all boards have this now) Dual 1gbit NIC's for teaming if your switches support it.

For MySQL if purely depends on how much usage it will be getting you could run the system on anything from a Intel Atom all the way up to Dual or more Xeon's.
It's all based around how many Queries are being run constantly on the database.
Usually this is where you would make some in house performance estimates on your needs prior to purchasing any hardware.

Ram plenty of Ram both File serving will use the ram for Caching and MySQL will use as much ram as you let it (once again based on your needs, could be anything from 4gb of ram to 16/32/64 depending on database size etc..)

For a system to be designed to meet your needs we would need some estimates on how much database usage it will be getting, how big the database is likely to be, how many users on the system etc..

Answers to your questions
1. Yes that should be fine, that depends more on your OS then the actual hardware involved.

2. Windows Server or Linux Server OS depending on your needs.

3. Both will work equally well, Rack is great is you have a Rack with available space for it.

4. Not necessary if you can live with a bit of down time while you replace the PSU int he machine. If not you can buy a dual redundant PSU that fits into the normal PSU hole space, have seen them might have to hunt around for them and they are not cheap.

5. Software and network configuration dependant only.

The database will only be used within the office. We'll have anywhere between 5-10 users accessing it at any 1 time.

The kinds of tasks they'll be doing are:
1) Editing/Adding products
2) Editing/Adding invoices
3) Looking up customer information
4) Changing/Updating customer information
5) Looking up order info
6) Occasionally running reports

For estimating MySQL load purposes, I'll say that I want the system to handle:
1) 8,000 - 10,000 products (Reality: We have about ~1,500 different "SKUs")
a. Each product will consist of product name, price, qty, color, description, product image
2) 100,000 customers (Reality: We have a list of ~30,000 "customers")
a. Each customer entry will have basic contact info and ship-to/bill-to address stored
3) 200-300 orders a day (Reality: About ~25-60 orders a day)

I don't know exactly how many queries the database will be running, but could you perhaps estimate with the info given above? Given: 5-10 users, the kinds of tasks we're going to be using the server for, and the size of the database.

Questions:
1) With this new info, is there anything in specific that I should be looking out for?
2) Can anybody recommend any possible builds?

Thank you

I went ahead and created a wishlist on newegg, can somebody please look over the parts and let me know if the build is adequate or if I'm missing some components.

https://secure.newegg.com/WishList/MySavedWishDetail.as...

Questions:
1) What is a "nic" and do I need this for my build?
2) Did I overspend/underspend on any parts?
3) Do I need more hard drives?