First it's will not be upgrade to that CPU. The motherboard has only an AM2 socket, not an AM2+ which the X2 450 could use. The motherboard specs list the X2 5000+ as the highest CPU it can handle which is what that system should have.
As for video cards, the 300 watt PSU in that system may be a problem as current era video cards like to feed on 12 volts. Both of those cards you list are rated around 50 watts maximum. The GT 430 should be around 50% faster than the 9500GT.
Father Xmas - Level 50 Ice/Ice Tanker - Victory
$725 and $1350 parts lists --- My guide to computer components
Tempus unum hominem manet
So the first one as mentioned is faster, can you explain what the 12 volts versus 50 watts means? I understand staying under the 300watts the system starts with, but not sure how that works with 12 volts, or what you mean it's rated at 50 watts maximum, that sounds like a good thing to keep the watt usage under that 300.
Plasmic's Guide to Sonic/Mental
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Sorry for being cryptic.
Video cards, in general, draw the majority of their power requirements from the 12 volt part of the power supply. Those two cards will use, worst case, 50 watts of power or about 4 amps at 12 volts. The CPU also uses the 12 volt part of the supply to draw it's power, the Athlon 64 X2 5000+ is rated at a maximum of 65 watts or 5.5 amps at 12 volts. So worse case, about 10 amps at 12 volts for the CPU and video card.
Edit: Just noticed that only some models of the 5000+ are rated at 65 watts, others older ones are rated at 89 watts. You can use CPU-Z to get the stepping/revision of the CPU. F3, G1 and G2 are the lower wattage variety, F2 is the older 89 watt version.
While the power supply in that HP is listed as 300 watts and the problem is the system specs don't list anything more than that online. Now there are some 300 watt PSUs with a 18 or more amps at 12 volts and some I've seen as low as 14 amps from HP/Compaq. You will have to crack open your case and look for the sticker on the side of your power supply to see what it can provide at 12 volts, more the better.
Or you can simply go for it, buy the GT 430 and give it a whirl. The specs from nVidia does say a minimum of a 300 watt PSU, you supposedly have that.
Father Xmas - Level 50 Ice/Ice Tanker - Victory
$725 and $1350 parts lists --- My guide to computer components
Tempus unum hominem manet
Ok, also forgot to mention Best Buy sucks, it was over a year before I noticed they gipped me and I actually have an AMD 4200+ not a 5000+ :/
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Plasmic Fire - 50 Fire/Rad Victory Server
Anyone have any idea how either of these vid cards would work with a HP M7750N desktop? More interested in the first one one cause of the HDMI connection that would work for my TV.
http://www.amazon.com/Evga-GeForce-P.../ref=de_a_smtd
http://www.amazon.com/EVGA-nVidia-Ge.../ref=de_a_smtd
And while we're at the notion of upgrading any idea how this processor would work and if it's good for it? http://www.amazon.com/dp/B003Z4PB3O/...80_pd_re_dt_d2
Plasmic's Guide to Sonic/Mental
Plasmic's Guide to Regeneration
Plasmic Fire - 50 Fire/Rad Victory Server