I have an Extreme Pro and would recommend this one since it's not terribly more expensive and you will be booting from it. The Mercury Electra 120GB is currently 65.99 while the Mercury Extreme Pro 6G 120GB is $91.75. You probably won't need this, as they have downloads available with instructions and they will provide excellent support in the unlikely event that you get stuck. You won't need to for a while, but they also provide upgrades for firmware/driver that are easy to install, or you can buy an inexpensive usb drive from them with the installer if you want 0 hassle. You can probably go with a 120GB SSD and I'd recommend an OWC SSD drive as their firmware obviates the need to enable trim for a non-Apple SSD. 4GB is really light if you are using the machine for anything but web surfing, word processing, spreadsheets, etc. I would update the RAM first if you can't just go for everything right away, preferably to 16GB. I have the same setup and I concur with danb1979. I bet within a year, we will see 1TB or 2TB SSDs at $0.20/GB, which will be quite affordable if you need it. Much later, third, I would replace the HDD with a second SSD (hence putting the HDD in the lower bay in the first step). DDR3 RAM prices are finally falling right now after a being stuck pretty high for a while, so the longer you wait to do this the less it will cost. Later or at the same time as above, second, I would upgrade the RAM to either 8GB or 16GB if you want to spend the cash. (Also totally optional and not for those who cannot afford the risk, while you have the MM open, if you're up for it on a technical level, I would also clean out and replace the thermal paste.)

Further, take this opportunity to clean out the Mac of dust. Put the SSD in the upper bay, and put the HDD in the lower bay, since the lower is easier to access later on and the HDD is likely the one you will want to access sooner. You can either set it up as a fusion drive, or keep it separate as a boot drive and manage which files are on which drive manually.

2012 mac mini ram upgrade