http://www.logicalincrements.com/
That should give you a general idea of what parts to get based on budget. Anything below 4 or 5 hundred dollars won't handle FTB very well and that does not include a screen, keyboard, mouse, or speakers.
The best value setup would be around the $1000 without the accessories I mentioned. The minimum for what you want would probably be the 5 or 6 hundred dollar range without the accessories.
Your right in terms of hardware, but there is nothing wrong with Windows 8 once you use it for a day or so. It can still do all the same things, its just a bit faster and has a few new features.
The question is if you want to buy all new parts or re-use some parts in your current computer. For example, if you like your current monitor, keyboard and mouse you're throwing away money by buying a complete system, as that $200 plus (depending on quality) could go into more ram, a faster CPU, or other feature that would improve current performance.
I've been building my own IBM type PCs since the mid 80s (and CP/m systems since the late 70s) and have found that it's not hard or expensive to slowly upgrade a PC as long as you are smart about upgrade paths and not insisting on "bleeding edge" performance.
Watch out for the various "religious" arguments out there... Intel vs. AMD, Nvidia vs. ATI (now AMD), etc. They can be misleading and not tell the entire story. A top of the line CPU is only as good as the mainboard chipset that supports it. Also, there are some major price differentials out there. I just saw an Intel I7 priced at over $1000 (I don't know how realistic the price was) while an AMD 8350 was about $200.
[edit] I second the opinion about Windows 8... I've seen better performance with it than Win7 on the same hardware... I ran both on a dual-boot configured system and saw substantial improvements in frame rate on the MMO I play, in MC and with streaming video when using win8.
In my personal opinion people that don't like Win8 are either unwilling or incapable of learning a few new methods -or- how to adapt win8 to look more like win7.