Need tips on what I should do with my PC build

[thymanbearpig]

Hello, I have one PC (custom built, specs are below) and I want two things.
I want to upgrade this PC, but also have a second PC.

I'm thinking of just upgrading my video card? I've been eyeing the R9 270 (idk if the 270x is worth it?)... I'd like to keep my budget small, and I made a rough idea of how much I'd spend doing an upgrade and a second PC. Came up with $400. Does that sound reasonable?
I want to play GTA V when it releases in Jan. and I only have a 19" 1600x900 monitor. I don't expect to max it out, but just something like high-medium settings. I'm also thinking of trying out Far Cry series and Assassins Creed series.. (any games I should try out? I've only enjoyed Valve releases, a little bit of COD - before BO2)

The second PC I'd wanna use like how I use this PC. I only play TF2 weekly and a couple random games that run okay-good.

*Current PC Specs*
Windows 7 Ultimate 64-bit SP1
Intel Sandy Bridge @ 3.10GHz
10GB RAM (I have two 4GB sticks, an extra 2GB stick, so I'm guessing I'm not running in Dual Channel, what would I notice the difference in?)
DH67BL
HP S2031 @ 1600x900
AMD Radeon HD 6670 2GB DDR3
320GB WD (I think I should upgrade this to 1TB and reuse the 320GB on the 2nd PC)

Exclude keyboard, mouse, CD drive, and OS. I need a second monitor but I can use a TV for now 😛

Thank you.

 

[smorizio]

if you do rebuild your pc with the 270. you could move the older gpu into the other pc. if you have a local microcenter they have the g3258 and mis z97 mb for 99.00 on combo deal. the intel msi z97 mb let you drop in a faster cpu if needed latter on. cosair r200/r300 case. standard dvd burner is 20.00 if your low on funds pick up a 8g usb stick and install windows 10 preview it free right now to use. look at black friday and cyber monday deals for monitors.

 

[thymanbearpig]

Nah I don't live close to a MircoCenter. Yea I'm thinking I can reuse my GPU, maybe one of the sticks of RAM? I forgot to include that my PSU is a TX650W Corsair, my case is an Antec Three Hundred, pre USB 3.0. I don't need a DVD drive or anything, and don't worry I got the OS covered. I probably will buy a monitor if I see one for $70? Is that an expectable deal? Thanks