Upgraded RAM - what do you think?

Hey all. I just ordered some new RAM yesterday. I'm just trying to get this computer running as good as possible and hold me off a while longer until I decide to upgrade to an AM2 board (currently 939). I picked up some OCZ platinum DDR400, as it seemed to be just about the best DDR400 RAM available, or at least close.

http://www.newegg.com/Product/Product.asp?Item=N82E16820227210

It'll be replacing some "value" Samsung DDR400 DIMMS that came with a pre-boxed gateway comp.
With the decrease in CAS latency and the heat spreaders, allowing better cooling (OC'able), it seemed like a good pick. I just hope that it works with my mb. Any reason to worry? Maybe different voltages?

Is it too late for you to cancel and then get these? http://www.newegg.com/Product/Product.aspx?Item=N82E16820148007

Yeah, those look cool too, but it's actually slightly more expensive. hehe.
They don't look like they handle heat as well though....Some ppl said they OC well, but someone also said that they get really hot.
Those OCZ's I ordered were shipped yesterday and are supposed to arrive on Monday.
My current setup is 4 x 512mb and I wanted to change it to 2 x 1gb, in case I even wanted to add more RAM. All of my DIMM slots are used currently. I know that the mb supports up to 4gb.

Just an aside question -- is having 3gb undesireable? Just wondering if you have to keep doubling when you upgrade: 1GB, 2GB, 4GB...
I seem to remember that with the really old school RAM (for Pentiums I believe), you HAD to upgrade in two's or it wouldn't work.
I would also imagine that keeping the same brand/model RAM is kind of a no-brainer, as timings and latency may be different.
Just wondering if someone can answer that. 2GB is serving me well, but just in case I wanted to add more. Not sure it'll be needed, but I'm just curious as to how it works.