There really are so many options available at just about any price point, it just comes down to the owner's specific requirements and preferences. What might be better here to help in establishing your best option is if we know exactly what you are wanting to budget. Maybe you are wanting to spend a little more than what it seems and from there you can move into a different type of platform. Perhaps you don't have as much to spend and there is a way to reuse parts from an existing system or find a way to use a slightly older platform such as the Core2Duos.
Are you planning on upgrading your present
computer ... or a brand new one?
More power and speed for less money by upgrading!
This also depends upon the current platform. The age of the socket/chipset types, the brand or quality of components chosen, as to whether or not it will save you money to upgrade an existing platform or if it would just be more efficient to purchase a brand new platform for a little more.
An example is a customer recently I had who wished to upgrade his existing
Dell desktop a bit. It was a Pentium 4 tower with 512 MB of memory with a 40 GB IDE hard drive. Granted, you can upgrade the memory to 2 GB of RAM for about $60, a larger capacity IDE hard drive for another $60, but then you still would have to be replacing the failing DVD-ROM drive for another $30 and the failing power supply for another $60. In the end, he's still running an out-dated chipset, single-core Pentium 4 2.6 Ghz processor, with a slower IDE controller and he spent almost half the cost of getting a brand new platform.
However, if the existing
computer is new enough to be a rather new chipset or socket type (such as LGA 775 or AM2+) then it may still be upgraded for a little less and still maintain a good performance level after the upgrades.