YOu can get a windows vps with plesk as you are familiar with it.
SATA should be fine.
Well as far as memory is concerned you should go with some provider witht whom you can start with 1 GB & later lets you upgrade if you feel you need more RAM.
Plesk, or you can go with Websitepanel which is FREE
I would say 1GB with 2 core, but depends on how big are you websites
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I'll echo on all above posts that Plesk is very stable on Windows with its 11.x version as I've heard no complains from existing customers. It was a different story for versions earlier than 10.x but they have started improving now. With regards to specifications, I'll always recommend starting with minimum 2GB RAM if you are going to have databases hosted on same VM as they consume good amount of memory (and they in fact perform best with as much memory available as it facilitates caching). You may also check with your prospective provider that you'll be able to grow and expand your VPS resources (RAM / CPU / HDD) seamlessly as your requirements increase in future.
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