Small upgrades to low budget gaming PC

Okay here is the deal. Me and my fiance love playing MMOs together. We have recently switched to Aion which is a bit more demanding on our PCs than our old MMO. So we are having some performance issues in the higher populated areas.

About a year and a half ago i built us new PCs with these specs.

PNY VCG86GTSXPB GeForce 8600 GTS 256MB 128-bit GDDR3 PCI Express x16 HDCP Ready SLI Supported Video Card
http://www.newegg.com/Product/Prod [...] 6814133198


AMD Athlon 64 X2 4800+ Brisbane 2.5GHz Socket AM2 65W Dual-Core Processor Model ADO4800DOBOX - Retail
http://www.newegg.com/Product/Prod [...] 6819103212


CORSAIR XMS2 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory Model TWIN2X2048-6400C4
http://www.newegg.com/Product/Prod [...] 6820145034


Western Digital Caviar Blue WD6400AAKS 640GB 7200 RPM SATA 3.0Gb/s 3.5" Internal Hard Drive
http://www.newegg.com/Product/Prod [...] 6822136218


GIGABYTE GA-M61PME-S2 AM2 NVIDIA GeForce 6100 / nForce 430 Micro ATX AMD Motherboard - Retail
http://www.newegg.com/Product/Prod [...] 6813128333

Both have 500 Watt Power Supplies

I'd like to do a small upgrade to each of these PCs with a low budget of around 200-300 bucks. I figure she cant get too angry at me for that.

I was thinking i could buy a new Mobo for her with 2 PCI 16x slots and 4 slots for memory, and take the memory from my board and put it in hers, giving her 4 gig. I could also throw my other graphics card in hers in SLI. Would she see a significant increase in performance from the SLI? Then I could pick up a new graphics card(preferably an ATI one) and 2 x 2 gig set of ram for myself.

Is this practical at all?

Or i could just get us both new graphics cards and 2 x 2gig sets of RAM and forget getting her a new Mobo.

Im just trying to milk maybe 1 more year out of these PCs then ill be building us brand new ones. She just doesn't want me spending a bunch of dough because she claims we have more important things to spend money on(like the wedding, go figure).

I'm very open to suggestions. I've been racking my brain trying to think of the best solution to my dilemma.

I'm sorry i wasnt clear, I basicly would like to get us both to 4gig of ram and upgrade our graphics cards slightly. I think the main problem we are having is those 8600s we have are only 256mb of ram.

We are both running windows 7.

The main reason i was thinking we needed 4 gig of ram is i notice when im running aion my task manager shows my memory at pretty much maximum.

So 2 of each

SAPPHIRE 100284L Radeon HD 5750 1GB 128-bit GDDR5 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card

http://www.newegg.com/Product/Prod [...] 6814102859

G.SKILL 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory Model F2-6400CL5D-4GBPQ

http://www.newegg.com/Product/Prod [...] 6820231122

Would be the best route to go?

I could do both of these upgrades for around 400

Or I could grab 5770s instead for 30 bucks more a card.

thanks for your help. My Processor isnt going to be holding me back too much is it?

Sounds great. You have been more than helpful.