CPU - Intel (i5 or i7)
OS Drive - SSD (Intel or Samsung)
Cubase Projects Drive (highly recommended to keep your recording drive separate from your OS drive) - Western Digital Blacks are what I use. No “green” drives! You want maximum performance, not power savings.
Samples Drive? - If you use a lot of VST instruments with large sample libraries it is recommended to have these on a separate drive as well. SSD is nice for this use, but also quite expensive.
General Purpose “storage” Drive? - If you are running a fairly small capacity SSD as OS drive, you will probably want a drive just to put general files on, Cubase project backup files, maybe your Windows Media Player library, etc.
Motherboard - Gigabyte or ASUS. Don’t be cheap here!
RAM 8/16 - either, but from your “hobby recording” description I would guess 8 would be fine. I can’t really recommend a particular brand. I’ve had good luck with Corsair, G.Skill, and Crucial.
OS - Your choice. Windows 7 is proven, but I know people are using Windows 8 successfully with Cubase 7. I’ve never used Windows 8. 64-bit all the way, here.
That should get you started. Without knowing your budget and more specifics on your recording/mixing demands it’s hard to get into further details.