Upgrade stock PSU (Dell 530 Inspiron w/ 300 watt PSU)

[nelmr]

Okay guys I have a Dell 530 with these specs:
Computer is 1.5 years old
Vista 32-bit
E6550 core 2 duo
HD 2600XT
4 sticks of RAM (1GB each)
1 7200 HDD
1 DVDRW
PSU is the 300 watt version. Looking online it appears to have 18A on the 12+V

I play these games:
Anno 1404
Age of Empires 3
Settlers 2 10th anniversary
TW: Medieval 2

Resolution 1680 x 1040

I have two questions:

1) If I replaced the HD 2600XT (which came stock on the PC) with a Radeon 4670 or the PNY Gefore 9800 GT EE do I even need to upgrade the PSU?
2) If I should upgrade the PSU what do you suggest?

 

[nelmr]

If I were to get this PSU:

http://www.newegg.com/Product/Product.aspx?Item=N82E16817341012&Tpk=OCZ%20StealthXStream%20500W

Would it work in my Dell 530 ATX case? The reason I ask is I see a fan on the topside whereas my current PSU has the fan on the back with the power plug. People online say this PSU would fit the dell but will it work well?

 

[Onus]

How many threads about this Dell do you intend to start today?
That PSU is not 80+ certified, so I would not buy it. Get an Earthwatts 380 if you want to upgrade your PSU.
And, PSUs with 120mm fans (or larger) are usually portrayed up-side down. Normally the PSU mounts with the fan facing down into the case (in cases where the PSU mounts on top); it can be mounted up-side down if desired, for example in cases where the PSU is on the bottom.

 

[nelmr]

Which one of these would you suggest for the ~$50 or less range?

http://www.newegg.com/Product/Product.aspx?Item=N82E16817182160 41Amp -$55
http://www.newegg.com/Product/Product.aspx?Item=N82E16817341017 42Amp -$55
http://www.newegg.com/Product/Product.aspx?Item=N82E16817139008 30AMP -$30
http://www.newegg.com/Product/Product.aspx?Item=N82E16817611007 46Amp -$50
http://www.newegg.com/Product/Product.aspx?Item=N82E16817611008 54Amp -$50

And which card would you suggest for $100 or less?

Basically if I bumped my budget up to $150 for a new card and PSU what would be the best investment?