Looking to do a new budget build and reuse some parts

[wwe9112]

So, I have a 1.5 year old child and another in the cooker . I work 80-100 hours a week. Needless to say, my budget is pretty strapped.  Anyway, I have a small home and don't want to get a rack mount. I currently have a poweredge r630 that sits on a bench in the dining room that I would like to turn into a giant desktop and hide away in a corner. That is all here nor there; however, hopefully that explains what I am wanting to do. 

 

It's tax season, the wife and I have 400-500 dollars that i can spend (though we would like it to be as small as possible lol). I'd like to do a new build. I'd like to reuse my drives (8) from my r630 (2.5 inch sas drives), but also slowly move over to 3.5 inch sata drives and maybe sas if hardware permits. I also have 3 3.5 inch sata drives that I run through a DAS at the moment. I'd like to keep those, too.  This would allow me to upgrade my drive sizes as I can.  What is a good build for this? I don't care about case size as long as it is a tower (even if I have to stack drives inside LOL). The tower will be up in a corner un-touched.  

 

Is this possible at all? How close to this can I get?

 

I'm also still on my trial of unRaid, would I be able to move my stuff across without losing the data / license? How would I do this? I'm currently mapping everything out. so I can attack it with a plan and knowledge. 

 

Thank you!