Avoid used stuff unless the seller is some one you really trust. With used stuff you never know what has happened with it, there might be some internal damage or tampering which would void the warranty.
With whatever budget you have get best possible basic components and then later on add stuff like extra RAM, Graphics card, SSD.
Processor -
AMD FX-8350 beats i5 chips when it comes to Photoshop performance, Photoshop CS6 makes good use of multi core processors and AMD FX-8350's octa core helps it perform better than the i5 chips. Softwares with support for multi coreprocessors for video editing, 3d modeling and video encoding would also be faster on the AMD FX-8350. But for all other applications and gaming the i5 is the clear winner. Choose the one depending on your use.
Motherboard - Get any ASUS or Gigabyte which has your desired features. If on a strict budget then go for the ones in the range of 4K or go for some mid range boards in the 7K range. If the motherboard has built in graphics then you can avoid a graphics card for now and later if you feel the need for it then you can always add one later.
RAM - Go for 4 or 8GB of RAM, if you feel the need for more then add more later.
Hard disk - Go for a 7200rpm Segate or WD.
PSU - A 500W Corsair should be enough if your not going for one of those mid-high end graphics card. You can use a online power consumption calculator to get an idea of how much power your system would need and based on this you can go for a higher rated model if needed -
Power Supply Calculator
OS - Go for Windows 8 home edition, it is available for 6K. Why do you need a Windows 7 Ultimate version? Do you need some ultimate version specific feature like BitLocker encryption? or else you can go for Windows 7 home premium which is available for around 7K but retailers hardly get stock of this version, so availability might be a problem.
If your budget is low for the above specs then you can always go for i3 or some Quad or 6 core AMD processor and save around 5K.
Prices of all PC components are set to rise because of the weakening Rupee, so you better decide and buy before prices rise
