Welcome to the forums. These two questions will make it easier to decide which is a better fit for you:
1. What are you going to be using this PC for?
2. What are your current system specs?
If you're building a new system the 1055T will be an overall cheaper solution with comparable performance to the i7-860 in non-gaming applications. If you're building a gaming box, then the 1055T might leave a little to be desired.
The core i7 860 will have noticeable difference over the X6 1055T in gaming.Overall the i7 is faster and also overclocks well, though the AMD platform will cost less.
Here is a comparison of the two: http://www.anandtech.com/bench/Product/147?vs=108
I have a x6 that I use for gaming and it's awesome. I've had no issues with any game and it's easily overclocked to 4Ghz with a good CPU cooler. I use a $40 mobo that I got for free when I purchased the CPU from Microcenter. If you are wanting to keep your existing DDR2 memory modules, I would still go with the x6. It is my OPINION at the time of writing this that you will have a better selection of mobo's that will support your ram.