[PC Gaming] Upgrades for Aion.

So I'm running an Intel core 2 duo E8400@3.0ghz, 3gb of ddr2 ram, 1333fsb mainboard and a pair of 9800gtx video cards (sometimes in SLI, sometimes just the one).

Playing Aion on 1680x1050 resolution I get between 40-100fps which I consider just fine. However whenever I get into towns I drop to about 20 fps in populated areas, and in castle sieges I drop to 8-10fps. I would prefer not to crank any of the settings down in game, and suspect I should be upgrading my processor and mainboard to compensate for the struggling system. I'm not overly concerned about price, and I'll probably stick with the 9800gtx cards and just upgrade the cpu and mainboard.

Would just upgrading the cpu and mainboard be wise, or should I be looking at upgrading the graphics cards also for this type of lag (caused by having tons of character models on screen at once). Or even should I hope they patch the game and I manage to see some performance increase in newer versions of the game/video drivers, seeing as I get really good fps running basically the rest of the game except sieges.

Thanks in advance!