HDD vs RAM upgrade...which first?

Faster ram does not scale well on performance. Moving from 1066 up to 1600 would be a decent upgrade, but it is not going to be a really big noticeable performance gain like adding a faster GPU. For the most part Ram is simply Ram, and so long as you have enough to prevent going into virtual memory (using your SSD, or God forbid your HDD, as system memory), then it should not be a huge issue. But the faster ram will increase your game FPS a little bit (my guess is ~10-15%), so if that is a specific need, then this would be the upgrade to do.


The HDD is only going to affect the programs and files that reside on it, so upgrading the HDD is not going to change your OS load time, or the load time of programs that are on your SSD currently, but getting a bigger/faster HDD will help with load times on games that are on the HDD. A faster HDD only changes your load time to get into a game, or load an area, it will not change the FPS inside the game one bit.
As an example; I got skyrim a while back, right before I got my first SSD (found it mistakenly on clearance at Target, I normally don't buy new games, but I couldn't pass up their stupidity lol). On the HDD some areas would take FOREVER to load, upwards of 20+ seconds for an area, which is ridiculous. Moving to the SSD brought all area load times down to 5-10 seconds which was nice, and more than playable. Now that I am running 2 SSDs in RAID0 the area load transitions are only 2-5 seconds, which really helps with the transition, and keeping me on the task at hand... though I have a lot less breaks to get up and grab a snack or drink now lol.

If your HDD is simply not full, then I would suggest a few options:
1) partition your SSD and use 60GB of it as an Intel RST cache for your HDD. The 1st 60GB or so would be for your OS and commonly used applications that you want consistently fast performance from. The 2nd 60GB would be used to cache your most used parts of the HDD, and if you start playing a different game, or using different files on a consistent basis, then it will adapt and follow your usage habits. If you do this, and you are not pressed for space on the HDD then you would not need to purchase anything (though you would have to deal with the annoyance of formatting, partitioning, and reinstalling all your software). But it would give you a little speed boost on some things, while freeing up your upgrade money for 8GB of DDR3 1600 (2x4GB kit by the way).

2) Get a 2nd identical HDD to what you already have (running mixed drives can actually yield worse performance), and then do a RAID1 to give you a little bit of redundancy for your files. It will also speed up read times a little bit (not a doubling in performance, but it will be better), which is a nice plus. RAID1 writes the same information to both drives, so there would be no performance boost to your write speed, but this is typically not an issue. In theory you could do this in addition to suggestion #1 and have a cache on the RAID, but I have never seen anyone do this and am unsure on how things would react (but it should work in theory).



The real answer is that you really want an SSD large enough for all of your programs, documents, and music collection, and then have a RAID1 or RAID5 array for bulk files like video, system/file backups, and files that you want some amount of redundancy on. So anything that you can do to move in that general direction would be the smartest move you can make from both a performance, and a data security/longevity standpoint.