Hey all I just need some help upgrading my video card. 

My PC while nothing special has been serviceable for some old school games, but my video card(integrated graphics) sucks. Lately I've been enjoying some gems such as Empire: Total War, CiV 3,4(humble bundle)! I don't need anything super fancy just want enough to play games such as Outlast, Amnesia, S.T.A.L.K.E.R, Company of Heroes, Rome, mainly RTS/Strategy/Unique games. I'm not looking to play Crysis or Battlefield just yet, although DayZ wouldn't mind.

So need some recommendations for a graphics card, biggest issue is I have a 0-100$ budget and am capped at a 300 watt power supply.

here's my PC's specifics: http://www.microcenter.com/product/405189/DX4870-UB21P_Desktop_Computer

Also I prefer a video card with no external wires if possible(just afraid that if I connect something extra I'm going to fuck up somehow). Thanks!

How much you willing to spend ?

I would just get a 6670 it's good enough, UK price is around £45

Just go find yourself an HD 7770. It's the perfect card at $100.

If you can find a 7770, 7790 or a R7 260, all those will fit that budget

Actually the 7790 starts at around $130.

First, you may have to upgrade you power supply. A 300w won't cut it for a R7 260x. Also, the new 265 was recently announced and the previous 260 and 260x will have a cheaper price point; therefore the 260 will be in your price range. Either way, it's recommended you upgrade your power supply.

If you don't want to upgrade power supply, then I'd suggest the R7 250. It should be fine for your needs (It will be much better than your integrated graphics and may not require a power supply upgrade).

A 300 watt power supply is enough. He has roughly around 150 watts to spare in his system.

Just a precaution. Card power draw can vary and spike, son he needs to go easy on the power rails assuming they are limited by given current. 

Just want to say thanks all, really anxious to upgrade my graphics. Now am looking to see the best one for me, hoping I could find one in a store near me so I can add it today.

Now essentially I want to stay around 300watts but going to 350 potentially even 400, I need to be a little careful?
I'm looking at the 6670, 7770 and R7 250 atm, trying to see if I can just pick one up today rather than order online.

This one I can definitely pickup today it's in stock near my house though I feel it's not what I should be looking for: http://www.officedepot.com/a/products/486583/Diamond-ATI-AMD-Radeon-HD-6450/ in terms of quality and pricing.