Split between PSU decision...

I've been looking to upgrade my computer the last couple of weeks, basically I was planning to upgrade my graphics card and replace the thermal compound/paste on my CPU with some AS5. Sounded simple enough, I suppose.

The graphics card I'm upgrading to is the AMD Radeon HD 6570 (current one is Radeon X1550).

I checked the requirements tab on AMD's website, and the recommended power that AMD recommended was 400Ws. Then I checked my PSU; it was only rated at 300W.

Now over the next two days I quickly figured out something about PSUs. My computer is a low-profile, small form factor case. It will only fit any PSUs of the TFX (thin form-factor) variety, I believe. There's not many PSUs for those! I have yet to see one that has been rated for 400w (TFX). Almost all are 300W or less even.

There's only two matches I've found that I can purchase, but I'm split between enough wattage vs. good quality.   Is 300 watts even enough?

Seasonic 300TFX 300w: http://www.newegg.com/Product/Product.aspx?Item=N82E16817151090

or

Athena Power TFX35 350w: http://www.newegg.com/Product/Product.aspx?Item=N82E16817338064

Essentially, would 300w be enough to power my system, or on the other hand, is the one by Athena good enough quality?

My system specs:
Motherboard: ASUS M3A78-CM
Processor: AMD Athlon X2 7750 Dual-Core (Socket am2+)
4gb DDR2 Memory (1gb x 4)
Hitachi 7200 RPM SATA Harddrive x1
DVD/CDRW Combo x1
AverMedia PCIe HD DVR (PCI-e x1 slot)
One 80mm fan (I -think- its 80mm) for the CPU. (and the new PSU would have a fan too)
Windows 7 x64bit

In any case, here's the one I'm currently using:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...