Hi all !
I am intending to increase the amount of memory of my back-up PC, and I have two questions (sorry if the questions are really basic, but I am far from to be an expert on these matters…)

I have one back-up PC with the following spec:
Processor – P4 2.8 GHZ 533 Mhz
MoBo – Asus P4SDX
Memory: 512 MB of Kingston DDR333 (Model KVR333X64C25) (2 sticks with 256 MB)
Video Card – Gigabyte Radeon 9600XT
Storage – Main HDD – Maxtor 120 GB ATA 133, 8 MB Cache, 7200 rpm
- Slave HDD – Seagate 40 GB ATA 100, 2 MB Cache, 7200 rpm
Midia: 01 Drive of CDR-W (LG) & 01 Drive of DVD (LG).

When I run some games that I like (mainly racing games), in some circumstances, the physical memory available reach the bottom line (around 15-20 MB). So, I think I can to deduce that my system has a bottleneck there…
I would like to buy more 02 sticks of 128 MB (so, my system would have 756 MB), and the memory should be from the same brand and specification. But, unfortunately, I could not to find it, so far… It seems very difficult to find here (in Brazil), these brand/specification with stick of 128mb… So, my questions are:
1) I need, necessarily, to buy new sticks of the same brand/specification? Of course, it would be the ideal, but, if I will not find it, would have some problem if I install new sticks of another brand (paying attention with the latencies of it)?
2) In order to maintain the Dual Channel working well, I need, necessarily, have more 2 NEW sticks of the same size (MB)? For example, currently, I have 02 sticks of 256 MB (total amount of 512 MB). Which would be the difference if I install ONE single stick more (same brand/specification), with 256 MB or if I install TWO new sticks (same brand/specification) of 128 MB each one? Would the first act (one single stick of 256 MB) to damage the POTENTIAL performance of my system (comparing to the situation in which I would install 02 sticks of 128 MB)? Would this single stick not to work with Dual Channel enabled?

Recently, I have changed, via BIOS, the latencies of my memories from default (2.5-3-3-7) to (2-2-2-6), and I felt that my system had a slight gain of performance (better results with 3Dmark_2001, PCMark_2002 and 3Dmark_2003). The system seems very stable (no problem so far); so, I would like to ask, too, if there is some risk if I maintain my memories with these more aggressive latencies… Is there?

Well, that´s it … Thanks in advance for any information!