Need a new graphics card, 300watt psu

APPROXIMATE PURCHASE DATE: ASAP

BUDGET RANGE: I'd say preferably under 150-200

USAGE FROM MOST TO LEAST IMPORTANT: Mid-range gaming. I mostly play slightly older games, and mid-range new games like starcraft 2. I'd like to run games like empire total war and Civilization 5. As you can see, I mostly play strategy games.

CURRENT GPU AND POWER SUPPLY: My gpu just died. It was a Geforce 7350 LE.
My power supply-
300watt, Not sure what all of it means, but this was the rail information on the side of it.
+12Va --- 18A 12Vb --- 18A
+5V --- 13A +5Vstb --- 2A
+3.3V --- 15A -12V --- 0.8A

It also said this stuff:

Power of 12va 12vb total 300W
Max continuous power equal to 350w (not sure what this part meant)

OTHER RELEVANT SYSTEM SPECS:
MODEL:m8120n

MOTHERBOARD: ASUS P5BW-LA (Basswood 3g)
here's the full motherboard specs
http://h10025.www1.hp.com/ewfrf/wc [...] ct=3440615

PROCESSOR: intel core 2 quad q6600

MEMORY: 3gb, ddr2, I believe there are 4 sticks, They're positioned behind alot of stuff so i couldn't get a clear look

VIDEO: This is what I need, the old one died

HDD:2x320gb 7200rpm Standard SATA

DRIVE: SuperMulti LightScribe DVDR/RW

Other stuff:
Memory card reader in front
TV Tuner- cable





PREFERRED WEBSITE(S) FOR PARTS: I usually use newegg, but any trusted site will do COUNTRY OF ORIGIN: US

PARTS PREFERENCES: Don't have much experience in this area, but any trusted brand will do. Will trust your advice in this area xD

OVERCLOCKING:No, i think probably bad idea with this power supply? SLI OR CROSSFIRE: Probably not

MONITOR RESOLUTION: 1680x1050

ADDITIONAL COMMENTS: I dont care about playing games with insane graphics. Just smoothly. I'd like the best graphics card that I can run on my current system.

I've been following this guide:
http://www.youtube.com/watch?v=LTQoH-j5KZY
and I've been considering the GTS 450, Radeon 5770, and Radeon 5670.

As Your PSU Is Rated For 300W Supply Only At The +12V Rails, The Best Card I Would Suggest Is The 5670/6670. They Come Under A 100$ And Do Not Require A 6 Pin PCI-E Power Connector. Thats The Best For Your PSU.

OtherWise Upgrade The PSU For 40 - 60$, Get Something Like A Corsair/Antec/Gigabyte 500W Which Is 80 Plus Rated, And After That With The Remaining 100 - 140$ Get The ATi 6770!