Adding extra 1 gig of memory - questions?

[Yardstick]

I'm currently running with 2 x 0.5 gig of Corsair Platinum XMS 3200 C2PT CL2. However, as I have recently picked up a X1950 Pro (AGP) and can how run most games with the settings pushed up to the max, game play is suffering from HD access stutters.

This rig only has another year of useful life left in it as my primary gaming machine but I would like to add an additional 1 gig of ram. However, I only have 3 ram slots and I will loose dual channel support if I do this.

Edit: I've just checked the mobo manual and it transpires I have 4 memory slots and have changed my questions accordingly. Also the ram is Corsair not Crucial - well I did buy it 4 years ago.

A few questions:

1) Will I get significantly smoother game play moving from 1 to 2 gig (stutters are most noticable in Oblivion, FEAR and Battle for Middle Earth 2)?
2) Can I mix another 2 x 0.5 pair of ram sticks (probably different from the original 2 sticks) and still retain dual channel opperation?
3) I assume that Corsair no longer make the Platinum C2PT sticks (mine are now 4 years old!), so what is the nearest match? I would like to continue to run the ram at CL2 if possible.

Athlon 64 3500+ (Slot 939)
Asus A8V Deluxe
2 x 0.5 gig Corsair Platinum XMS3200 C2PT
X1950 Pro (AGP)
SB Audigy 2

 

[subxero]

1. Yes
2. Yes
3. See if you can find some memory with the same timings or at least the same cas latency.