thanks for the replies. so should i go for the GPU/PSU upgrade first? will my core 2 duo E7500 be enough to handle the future games and applications? im also worried that my cpu will bottleneck those GPU's mentioned above.
btw my budget is going to be only $300. that's why im stuck at those choices listed.
There are usually better options than the Cooler Master GX series for the same, similar or even cheaper in price. AznShinobi just showed you one, it is even powerful enough to crossfire 6850s. It doesn't come with a power cord so just reuse the one you are currently using.
Even if your CPU does bottleneck your GPU, it doesn't sound like you are planning to keep the CPU/mobo indefinitely, so the new GPU should be a nice boost in performance anyway until you can change the CPU/mobo.