[Solved] Need some TIPS for choosing my first GPU???

Specs.............................................................................................
NEW SYSTEM--- currently running windows XP pro-32bit (will be running WINDOWS 7-64bit a few days after its release)
CPU------------- AMD Athlon II X2 245 Regor 2.9GHz 2 x 1MB L2 Cache Socket AM3 65W (I overclocked it to 3.72 Ghz about 2 weeks ago)
Memory--------- G.SKILL 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 1066 (PC2 8500)
Motherboard---- GIGABYTE GA-MA785GM-US2H
Harddrive------- 500GB 7200 RPM 32MB Cache SATA
Power supply--- 600watt
Monitor--------- 20inch LCD widescreen (1680x1050)
GPU------------ HD 4200 (onboard video)
........................................................................................................

I am looking to spend $100 max on a graphics card at newegg.com
This is pretty much the best game i will be running http://www.totalwar.com/empire/?t=EnglishUSA
MY motherboard....................
http://www.gigabyte.us/Products/Mo [...] uctID=2997
MY power supply ................... (the power supply has a 6pin for a GPU)
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The BEST screen resolution for the monitor i have is 1680x1050

I have picked out these GPU's cause they seem to be pretty good???
(pretty much i just need to know which one won't rape my MOBO or PSU)

Radeon HD 4850 512MB -- $95 (REQUIRES 6PIN) (i like this one the most so far, but it might be too much for my system)
http://www.newegg.com/Product/Prod [...] 6814102824

Radeon HD 4670 512MB -- $70 (powered by the motherboard)
http://www.newegg.com/Product/Prod [...] 6814125244

Also is there a way you can check if the card is compatible with the MOBO or does it just need to be a PCI Ex16??
What's the sound lvl of these GPU's???? My computer is pretty quiet so i need a GPU to match it.. (if possible)!!

I play mostly strategy games..!! (controlling tons of troops and stuff like that)
Right now with the on board video (ATI Radeon HD 4200)
Empire: Total war - (need more graphic power) -- Release Date: March 03, 2009
Rome: Total war - (runs OK) I can have 18,000 troops in one battle without lag at med graphics -- Release Date: September 27, 2005
Blitzkrieg 2 (runs GREAT) full settings -- Release Date: February 20, 2007
Stronghold 2 (runs GREAT) full settings -- Release Date: April 19, 2005
Gettysburg (runs GREAT) full settings -- Released Date: April 28, 2005

I DO NOT NEED MY GPU RIGHT AWAY... I'm just trying to narrow down to the BEST GPU for my system at $100.
Sorry for the long post but i want it to be detailed and clear for the PROS out there!!!

hey friend thank you for sharing information. it will definitely helpful to beginners.

I agree with teh 4850 i think it will be fine with your system

Mactronix