Is the one that matches your wallet.
As regards which IDE/SATA etc., the same as you have in there - that is what the MotherBoard is set up for.
Apart from that the world is your oyster.
All the main makes are as good as each other in reality though will hear opinions for this or that..
So scan the Box shifters and get the biggest you can afford.
When you get it partition it 33/66% put the op sys and programs and active docs on the small part and use the large part for storage.
As regards th ailing drives - get every thing off SAP.
If they are dying there is not point in putting stuff on them is there?