Looking to buy a new pc, suggestions/advice?

K, so i’m going to replace my old pc. I’m just looking for some advice on the type of processor and vid card i should get. 2 things, i’m not going to get a custom pc built, so don’t bother telling me do so and i’m not going to be purchasing online. So that limits me to best buy, circuit city, compusa and microcenter. Now, i’m looking for something in the $400-$750 range. The pc i have now is an amd 64 3200, i’ve been looking at processors for the past few days and it seems like the top cpu’s out now are the Phenom (amd) and quadcore (intel).

First off a few questions. I’m curious to how the multiprocessors work. Would having a dual core of 2.0 ghz mean the processing power is 4.0 ghz? tri-core of 2.0 ghz = total cpu power of 6.0 ghz? Also out of the 2 companies, who is making the best most reliable processor right now? And please, try to be as unbiased as possible.

Q6600 with 2 ATI 4850 2 GB version.

http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=2643933&Sku=CP2-DUO-Q6600 <-- Processor.

Asus P5K3 Deluxe WiFi Intel Socket 775 ATX Motherboard <— Best Mobo!