If you are looking for something in between a full blown MRP system and an Excel spreadsheet template, I highly recommend checking out a software package called "Parts & Vendor ECO Edition" (
I have used it in several small companies (under 50 people) and it works great.
It does not tie into your accounting software directly, but it does track your parts and vendors, manage your BOMs, automate component and assembly revision control, generate purchase orders,etc. I have used it from both the designer side and management side and it's a great little software package.
The ECO version has everything you are looking for and it's very simple to use.
It's moderately priced ($350-$450 per user license, depending on how many you get)and pretty easy to implement from scratch. It also pretty straight forward to import your current data and get started.
I am in no way affiliated with Trilogy Design, but I do appreciate a good tool when I find one.
Check it out and good luck.