1st thing I would suggest is getting a SSD to run as the OS drive. Then get a second drive and keep LB and your roms and emulators on that. A 7200 rpm Drive will definitely preform better than a drive with slower revolutions but in my experience the 5400 rpm Drive should be just fine. Depending on your needs 4TB would be fine although I would go bigger these days as the price of 6TB drives is around the same for what I payed for all of my 4TB drives but that is me and I'm a data hoarder