Alright, I just wanted a ballpark figure, I could give you a parts list that would total several thousand dollars but would run FTB at a few hundred frames a second no matter what.
I will put together 3 builds, 1 with no price limits, 1 with a limit of $2000 and another with a limit of $1000.
Edit: Price no object list done:
http://pcpartpicker.com/p/XOW7
It is basically the best parts money can buy. Running FTB on this thing would be like using a bomb disposal robot to squish an ant, it can FTB and so much more, likely at the same time.
Edit 2: Near $2000 build done:
http://pcpartpicker.com/p/XP58
This is still a very powerful machine, but with some excessive things like the 2 SSD's for Raid 0 removed. The FPS would likely stay the same, as it also drops the screen resolution and price.
Edit 3: Near $1000 build done:
http://pcpartpicker.com/p/XPdj
This is the lowest you likely want to go. The key differences include a noticeable drop in screen quality, and no Windows 7. If all your doing is running FTB, then using Linux is free and works great. It also cuts down on storage space, memory, a custom cooler with excellent fans, and drops the CPU and GPU tier by one basically. This is a no frills machine with plenty of power for gaming, but it doesn't include high quality peripherals. My personal computer is almost identical, I would say expect 100 FPS running on Far render distance with everything else default.
Edit 4: I just noticed you edited your post above about the graphics card and wherever you were/are going to buy that computer is not seeming trustworthy. ATI mobility graphics are quite old, several years ago the branding was turned to AMD. Also, laptop video cards can not be in a desktop or vice versa. I assume you copied the info straight from the place where it is being sold and if so, that information is false.
The following link is a pretty good guide to building a computer.
http://lifehacker.com/5828747/how-to-build-a-computer-from-scratch-the-complete-guide
Aside from performance, how a computer is put together hasn't changed all that much in the last decade.
If you need any more help or have questions, feel free to PM on these forums, I can also be found by the same name on Steam, Skype, Reddit, almost anywhere really.