Hah, I have the same setup as you. I thought the same thing as you too. Ok, so I have good news for you have not so good news.
You currently are using the 2nd best socket 939 processor. There is only one more better than the 4800+ before they discontinued 939 and switched socket types to AM2. That is the Athlon FX-60. However, shoota is correct that you should read that other article. If you like to play games as I do on max settings, upgrading to the FX-60 is NOT going to mean better framerates. You MIGHT get a +1 or +2 fps with the FX-60 compared to the 4800+ if you play on max settings. Read the article. Not worth it getting the processor upgrade.
Ok, onto ram and video card. For your ram, 2gb is ok, that is what I was using. 4gb might be a bit better, but if you are sticking with a 32-bit os, ie windows 32 or vista 32, you will only be able to use 3gb if you stick 4gb in. o.s. limitation. Nothing you can do about that unless you go to 64 bit windows xp or vista64.
For the graphics card, yes PCIe 2.0 is backwards compatible. I'm pretty sure on the a8n32-sli that both pci slots are full x16 and are pcie v1.1, which means I think sli would work with two 2.0 nvidia cards. However, there have been problems reported in the past that having a motherboard with a v1.1 on the first slot and v1.0 or v1.0a on the second slot that that difference would prevent you from putting two 2.0 cards in the system as it would fail to recognize one of them. I know the 1st pcie slot is v1.1. I THINK with the a8n32-sli the second one is also (though on the normal a8n-sli board, I think the second pcie slot is v1.0). However like I said I think with the a8n32-sli you are fine.
As far as the best video card for you, your BEST bet is installin a 4870X2 into your system. Its really powerful, and may require you to get a different power supply with different connectors into your system. Honestly though, shelling out $500+ for that card isn't worth it. You can pick is a 4850 off of newegg for around $150 bucks. This ONE card will KILL your dual 7800 gtx's in sli mode. The performance difference you'll see by this simple updated is phenominal.
The 4850's performance compared to nVidia's latest GTX260 and 280 are sooo minute, that the additional benefits from DirectX 10.1a that you get from the Ati card is sooo worth it. Once again though, you can't use DX10 with windows xp though, so you'd have to switch to vista to get that.
With that said, my recommendation for you is almost the same as what shoota recommended (and its the same I did to my system!), is buy the HD4850 from newegg, get yourself 4GB of ram instead of 2gb, and upgrade to windows vista64. You'd be able to use the full 4GB of ram, you'd now have DX10.1a support in your gaming, and with the ATI card 10.1a directx means you will get even better graphics than the nvidia card (granted, the difference is not HUGE, but I have 2 systems here once using ati and one using nvidia, and within Warhammer I notice a major difference with the ATI card and how the darks and shadows look a lot better. The nvidia card looks more bright and cartoony like WoW.
Ok, onto the not so good news. A LOT of people have been having performance problems with Warhammer. Even people with the latest and greatest best of everything $6000 systems. This is a WARHAMMER issue, not a system issue. So the 'studdering' issue you are seeing might not have anything to do with your current system anyway (though I still recommand the upgrades!) They recently released a patch that toned this down a bit, but its still noticable. I was able to *almost* get rid of this studdering by changing some settings. I think it was turning off grass and off or down something else too and kept everything else at max...can't remember what off the top of my head. It *sounds* related to system performance, but everyone across the board, doesn't matter what your system is, is experiencing the same issue. Just google 'warhammer studdering' and you'll see what i mean.
Hope that helps!
Facebook
Twitter
Instagram