Advice about maximum amount of ram recommended

I have the M4A785TD-V EVO motherboard, which has 4 dd3 1333mhz slots, and each pair of them support functioning in dual channel. At the moment i have 1 kingston stick of 1gb (KVR1333D3N9/1G) CL9, and 1 kingston stick of 2gb (KVR1333D3N9/2G) CL9. Note that usually i have tons of programs loading at startup and i do a lot of multi tasking.

I really need some advice here, i don't know if i should go to have as much memory as possible (6gb-8gb) so that i don't have to worry about buying more in the next 5 or more years regarding intensive gaming or the windows that will come next to seven in 64bits. I say this because so soon i don't want to have a computer using lots of virtual memory, if in later years the new windows that will come out asks tons of memory or the games themselfs, much like windows 64bits is doing in relation to the 32bits versions.

Another problem i have is, if i buy 2 x 2gb sticks, if keeping the original two sticks working at single channel will affect the performance of the new ones, even if they all work at CL9-9-9 and they are in different channels...

And at last, i ask the same question as above, but in the case i choose now a different brand of sticks other than kingston and which one you recommend...

I always buy ram in pairs to avoid issues (YMMV), being doing this for years, I recommend selling both sticks and get a 2 x 2gb matched sticks.

I always buy ram in pairs to avoid issues (YMMV), being doing this for years, I recommend selling both sticks and get a 2 x 2gb matched sticks.

Hum... i think i am going to actually do that, yeah that's probably the best idea, BUT i will still see if there is any change in the speed of the new dual channel pair, if by keeping the older 2 sticks the speed/performance isn't changed in benchmarks on in memory speed testing sofware then of course i will prefer having 7gb memory :)

The main reason i won't sell the older sticks is because specially the 2gb one, now it's price is TWICE smaller than it was at the time i bought it, so i am not willing to get rid of it that soon, specially because i have a lot of trouble finding someone to buy used stuff from me, and generally i don't have much luck with that.

There is another doubt now... in case i choose other brand than kingston... considering i would buy also cl9 memory, would be notice any difference at all ? Because if by choosing other brand of memory i wouldn't notice much difference then it's best to stick to kingston in case the performance doesn't lower by keeping the 2 older ones.

Yeah but these two i have are all CL 9-9-9, and the new ones i see in online stores all say the same as well... and i mean, both 1gb and 2gb versions of them. Is judging by the CL9 indication enought ? If i buy them i would have three KVR1333D3N9/2G and one KVR1333D3N9/1G, and they all have CL 9-9-9, don't know if this is enough to have an idea if it would cause problems or not... Also i am using a 32bit os now, but the only thing keeping me from upgrading to 64bits is because even by having 3gb at the moment, sometimes i have virtual memory problems...

The other option is getting three more sticks of the same Kingston 2gb ram.

This is more like the option i am thinking at the moment, since the corsair option is more expensive, even tough there is the added risk of the 3th stick not being compatible with the old 2gb stick even tough they have the same model reference and CAS latency, the problem is i don't know if this is worth because tell me, there isn't much difference in having two pairs of 2gb sticks in dual channel when comparing to having one pair in dual channel and the other one in single chanel one of them being 1gb and the other 2gb, sure there is one 1gb less but would this worth the risk then?

Anyway now my only doubt is that one, it's more like if i buy that 3rd 2gb stick or not, probably it wouldn't make that much difference and i could save some money like this.