Upgrading RAM on K8V Deluxe

Hey everybody, I've had my system for about 2 years now, and I'm about to do some nice upgrading to get back into the game.

I currently have:
Asus KV Deluxe VIA K8T800
AMD Athlon 64 +320 (Clawhammer)
1g Corsair XMS DDR 400 PC-3200 RAM (512 x 2)
Geforce 4 TI 4600

The reason I'm here, is because it has 3 slots for memory. I vaguely remember sometihng saying you had to "pair up" memory on either this chipset or because of the CPU or all the sticks had to be the same size.

I'm hoping to just buy a 1g stick and put it in the 3rd slot. But will I have any compatibility issues? Or will it just act like I have an extra gig to use?

Thanks in advance.