P5B Deluxe Noobie Memory Question

[iqwertyi]

Hello,

So, purchasing my components a little at a time.
I got my E6400 and P5B Deluxe, now looking for memory.

I've never overclocked and will probably not do it for this one. BUT, I'd probably like the option to do so, just in case I want to dabble with overclocking down the line.

So, I think the DDR2-667 or 800 is probably the way to go.
I'd like to spend about $150, which will probably only get me a gig of memory (if that).
First question is, any recommendations? (besides what's recommended in the Asus manual)
Second, Is it better to go with ONE DDR-2 in one slot or TWO DDR-2 in two slots? (i.e. One 1 Gig stick or Two 512 sticks?)

Thanks all