512 PC3500 to 512x2 PC4400 how much benifit?

[Codesmith]

I just upgraded and I kept my Corsair XMS 512 PC3500 memory from my old system.

My new system is an MSI Neo 4 Platinum (Nforce 4 non-SLI), and I am running my memory at 400mhz 2-2-2-10.

I can't buy another module and run my memory in dual channel mode according to Corsairs "Ram Guy".

My Options are to buy 512 value memory for my old PC or upgrade to 512x2 for my new PC.

I can OC my MB stable to 240 FSB, which lowers my memory to 392 mhz. (I think I am being held back by SATA drive and/or my unwillinges to run high voltages).

I just bough a ATI x800XL to play halflife 2, doom3 and other new games.

Questions

1) How much benifit will I see in games/divx encoding/everyday use from 1GB dual channel vs 512MB single channel.

If anyone has done benchmarks with one stick of a dual channel kit removed please tell me how much differnce there was.

2) How much actual benifit will I see running 400mhz 3-3-3 vs 400mhz 2-2-2 vs 480mhz 2-3-3-10
2.75V 1T

The price difference between the Corsair Value CP3200 ($108 400mhz 3-3-3) and the XMS 4400 ($270 480 mhz 2.5-3-3 @ my current settings) is quite large, I am just wondering if its is worth it.

 

[Codesmith]

Its rated at 434 2.5-3-3 1T @ at its normal voltage (which might be 2.7v?)

I am trying to talk my friend into removing one of his 512 modules and playing halflife 2 and see if he notices anything.

Its dual channel 400mhz 2-3-3, or better yet I visit his house and try it myself.

If I see a huge differnce in half life then I might upgrade.

Otherwise my 2nd PC gets corsair value memory