What parts of my gaming PC should I look to upgrade first?

Any experts here? I have recently built my first PC, which is for gaming, but it was mainly my neighbour who is good with computers that did the crucial bits. I know I'm getting a bit ahead of myself by thinking I should upgrade my computer when it's not even a week old yet, but I'm just looking about on the Internet for possible future upgrades. Here are my specs:

AMD FX-8350

Radeon R9 270X 2GB GDDR5

2 X 4GB RAM

1TB HDD

Integrated sound

Network card 300mbps

600W power supply

Motherboard: http://www.dabs.com/products/asus-m5a97-r2-0-am3--amd-970-ddr3-atx-87SZ.html?refs=473460000&src=2

Windows 8.1

I was thinking of upgrading to 16GB of RAM by adding in another 2x4gb of the same stuff already in there, but apparently since most games are written in 32-bit, the game can only use about 3 or 4gb of RAM.

I'm also thinking of adding in a 256GB SSD. It was a recommendation from my neighbour since it would load the operating system faster. Should I get this first? Also, I'm worried that if I get 256GB I will start to use the SSD for saving everything, so it would be like my HDD was a waste. Should I instead get a 64GB SSD, and only use it for the operating system? Just say what you think.

I was also thinking about crossfiring 2 of the same graphics cards together, so my machine will be futureproof for a bit longer, but I think there's a problem. I don't think my power supply has enough power cables to power 2 graphics cards! It's crazy enough how the one graphics card in there requires power not just from the motherboard, but 2 extra slots on the top of the card!

Anyway, is it worth it to do this or will my current card last me at least for a couple of years? I don't play battlefield because I'm too young, and I used my real age so Origin doesn't let me, but I play Rust on max settings on a monitor about 1400 x 900, and there's no lag. I may play GTA later, and I've read that a 3GB or 4GB graphics card is just overkill, much like the i7 processors, so will 2GB do it on maximum graphics settings?

I'm saving up for an HD monitor. At the moment on my current monitor (lended to me) with a resolution of about 1400 x 900 (I can't remember exactly, I'm at my dad's house on my laptop so I can't check) I can play Rust on maximum settings, and I can run Minecraft on maximum settings on amplified biomes at a steady 60FPS. Will these games lag a bit if I start playing on an HD monitor?

Thank you to anyone who took the time to read all of that!

Added (1). Also, just to let you know, these upgrades won't be happening straight away because I'm getting some speakers first, then an HD monitor, then I will probably wait for a while to see how the PC goes before upgrading.

I'd go for the SSD and reinstall Windows in a hybrid setup with the /users and /program data folders redirected to drive D:

That gives you all the advantages of SSD for speed of program loading etc., but stops it filling with the normal accumulation of stuff in data directories.

See the link here for details:
http://answers.microsoft.com/...56aebb296e

You will have to edit the XML snippet if you are using something other than WIn 7 ultimate.

I use this as a standard setup on all machines I build with SSDs (for both gaming and business CAD systems etc.) and the overall performance of the machines is excellent.

A 64gb ssd is not enough for your win8, games and programs installation, a 256gb ssd will do.