A lot of people have had very impressive results using Xenadrine, but at the end of the day it works in different ways for different people. Yoiu'll only know how well it will work for you once you try it.
I've been using it for 4 weeks and am having very good results.
Do a search using the keyword Xenadrine and you will find loads of threads relating to it.
If you want to refine the search by using keywords "Xenadrine" as well as "cheap" you will probably find the best places to buy it.
Hope this helps.