Finally, someone talking some sense. For the OP's stated uses, your e8400 will do you quite well. Quads are nice, but not worth the upgrade price. Wait until (if ever) you need notably better performance. For surfing, that day may never come, for even moderate gaming, it might but then may also be handled by a GPU upgrade. To anticipate just about any single graphics card (all but HD5790), make sure you get a quality 500W-550W PSU. Look for full range active PFC (no little voltage switch) and at least 80+ certification. Antec, Corsair, PC Power & Cooling, Seasonic, and Enermax are among the better brands.
Anyway, you say you're about to change your processor. Why? If overall budget is the concern, then AMD pretty much owns the budget segment. A competent web surfer can be built for <$400. If there's a program you have listed that demands more performance, then Intel is your best choice. Something like an i7/860 on LGA1156 would be nice.