NAS & Multiple Libriares

Greetings!

If my topic is vague in any way, please let me know and I will do my best to clarify.

What I am trying to accomplish is me and my wife each have our own iTunes accounts. Her's on her laptop, and mine on my main computer. Recently her computer has dramatically declined in performance and her hard drive has filled up. My computer on the other hand is pretty speedy, but I am aiming to keep it for gaming purposes only.

I am currently running my network off the Airport Extreme. While I am not all that familiar with apple products and software, I was pointed in this direction, for ease of access control (which it is).

I have recently transferred my itunes library to a regular run of the mill USB external hard drive that I have plugged into the USB connection on the router. My itunes synced to it without any issues. With my wife is now starting to take some online classes and having to use her computer on a more regular basis, I transferred her iTunes to a second USB external hard drive to help alleviate some of the pressure on her hard drive to help her multitask easily. I plugged her hard drive into the router using a USB hub, so I could have my hard drive and she could have hers. Hers synced without any issues to the external drive. The one main issue I am having now with the hub, is each time I turn on my computer or she turns on hers, it reconfigures the drive names. Originally when I set this up, my hard drive was drive Z and hers was drive Y. Now from time to time, Mine will by Y and hers will be Z. This has become quiet an annoyance as each time I am playing a game and want to listen to my music, I need to re-assign the medial folder.

With NAS (Network Attached Storage) drives becoming cheaper, I was hoping someone or someones could direct me towards one that I can put the library from her hard drive and my hard drive on one, and manage to keep her iTunes and mine separate. To me it does not matter if the merge, but to keep her happy she would rather have them separate, but still share them using the Home Sharing option. Also, if it helps with pointing me in the proper direction, I am hoping to not spend more than $150.00. Is it possible to put both libraries on one USB hard drive if naming the folders two different things to keep them seperate or would going the NAS route be the way to go?

Any assistance in this matter would be great! If any clarification is needed please let me know!

Thank you!