Actually,many of the prices at Scan can be cheaper than those on Ebuyer and you get free next day postage with Scan too. Scan also has daily offers on items so you need to check the Today Only and Shop Offers webpages too.
Many RTS games can run better on triple and quad cores. Hence, in games which scale well with more cores the Athlon II X3 will be faster whereas in games which run better on two cores the Phenom II X2 will be faster.
The HD4250 integrated graphics on the 785G motherboards are much slower than a 9800GT. If you intend to play any modern games then TBH you need a get reasonable graphics card.