Hi Clint,
I just picked up this
512GB to replace my 128 SSD boot drive. I think this is the best bang for your buck currently. You could save money and go with a 128GB drive. I am now using my 128GB in the external enclosure we talked about. With ST3 and Omnisphere samples, the drive has little left, so it goes fast, hence my suggestion to go with the 512GB if you can swing it.
Here's the
external enclosure I'm using. It comes with the USB 3 cable (you need a special cable to get the USB 3 speeds, but any USB cable if using USB 2).