Elite ECS RX480-A vs. ECS RS482-M vs. Asus A8N-SLI Deluxe motherboard?

Last week I bought an Asus A8N-SLI Deluxe motherboard for $120 and a
AMD Athlon 64 3500+ for $170 from Fry's. I wanted to get the 3500+
anyway, and it was $170 instead of $200 if I got the ECS RX480-A with
it. So I now have a ECS RX480-A mobo I may never use.

First, I'm trying to decide if it's worth keeping the Asus A8N-SLI
Deluxe mobo for $120 or if I should return it and use the ECS RX480-A
instead? Or would it be worth the trouble to exchange the RX480-A for
the RS482-M for the same price?

All I care about is game performance, especially Doom 3, Half Life 2,
Battlefields 2, Unreal Tournament series, etc.. A few percent of
performance difference isn't worth bothering with, but 10-30% probably
would be.

I did feature comparisons on these 2 ECS boards, and the RX480-A
supports more memory while the RS482-M has onboard video (which I
doubt would be anywhere as good as a Geforce 6600), so the feature
differences don't matter to me... only game performance. All I know
from searching on Google is the RS482 chipset is newer and supposedly
better than RX480, but I don't know by how much.

Can anyone give me some opinions on which of these 3 motherboards to
choose for game performance?

Finally, I'll mention I got a Manchester core (E4 stepping) instead of
a Venice core (E6 stepping) in my A64 3500+. Someone told me the
difference in speed and overclockability (hopefully I can get up to
2600 MHz) should be trivial between these 2 cores, so I plan to keep
the Manchester unless someone tells me the performance difference is
significant.

Regarding my system as it stands:
- A8N-SLI Deluxe
- A64 3500+ with Manchester core (X2 with 1 core disabled)
- 1 GB PC3200
- Geforce 6600 PCI-E
- Windows 2000 SP4

My only disappointment is that games like Doom 3 are still not jitter
free. Most of the time they are fine, but every 10-30 seconds there
will be a slight jitter or pause as I move around. I don't know if
everyone else experiences these jitters or it's just me. I thought
this system would be enough. Since this is a brand new install and I
only have the minimal drivers/applications installed, I doubt I have
anything interfering with the CPU to cause the intermittent jitters.

Any help would be appreciated. I'm sorry this post was long.

 

I am quiet sure that the 6600 is too slow, but that depends on the
resolution and details of the game. An additional GB Ram would not be
bad, too.
Rennie