Best SSD upgrade for my Asus M32 Desktop?

[MPLumos]

I have a $150 gift card to Dell.com and wanted to add a SSD to my recently bought Asus i5-6400 M32CD Desktop. It has a 1TB HD and 8GB of ram currently.

I wasn't sure what my best option is.
My restrictions are that I'd like to stay close to the $150, and I only really want to put the OS (Win10) on the drive, and keep the installed 1TB drive for storage. (I also have an external 2TB HD for storage.)
I don't do much gaming, so a 240GB size would be fine, but is it possible to get a larger SSD for the money I have? Thanks

Update - I've narrowed it to between these:

Samsung 750 EVO (500GB)
Model MZ-750500
http://accessories.us.dell.com/sna/productdetail.aspx?c=us&l=en&s=dhs&cs=19&sku=A9010284

SanDisk Extreme PRO (240GB)
Model SDSSDXPS-240G-G25
http://accessories.us.dell.com/sna/productdetail.aspx?c=us&l=en&s=dhs&cs=19&sku=A7954703

Any input? Thanks

 

[popatim]

You'll be able to get around 500gb for that much