Heres what I would buy for 800$.I wont show you benchmarks,since i assume you wouldn't know much about hardware/numbers.Also it would be good to know What speed ram?PC 2100,2700,3200
CPU Athlon 64 3000+
http://www.newegg.com/Product/Product.a ... 6819103537 This would be atleast 100% faster than your 1.3ghz.which I assume is a AMD cpu?
Nvidia 6600GT
http://www.newegg.com/Product/Product.a ... 6814130220 I stand behind this card its about 20-30% faster than the last gen fastest card 9800Pro.
Motherboard
http://www.newegg.com/Product/Product.a ... 6813130491 Since you dont OC its a soild brand.
Ram
http://www.newegg.com/Product/Product.a ... 6820146883 OCZ is very trustworthy.Ram is dirt cheap right!!Damn I need to buy some myself.
Thats 495.99$ Also I assume you could sell your old stuff to help with the new PC's cost.300$ left for more stuff.You want a new hard drive?DVD-RW drive?That would be maybe 200$ more.Although if you cannot build a PC.then your fooked.....Just kidding.Ill search for a On line builder to help you.Also I may be interested in buying your Mobo,Card,CPU.
If Thats all you need to have a new PC,But want to spen the last 300$ then i could recommend faster parts.