RAM, integrated memory and HD upgrades

I asked a RAM related question before on this board I think, but something else occured to me. First, I am definitly upgrading to at least 1GB, 256 is obviously just not enough. But, I've always heard upgrading past 1GB of ram doesn't really yield useful results. However, I didn't consider the fact that my system uses shared memory with the video. I want to have the full 128mb devoted to my video, so would upgrading past 1gb be beneficial, since its shared memory? Maybe not upgrade to a full 2gb, but put in a stick of 1gb, and keep in one of the old 128mb sticks? (theres currently 2 128mb sticks filling both ram slots) This way a full 1gb would be devoted to my system, while still allow the full 128mb for my video. Will combining ram brands/sizes like this produce unstability? Thanks for putting up with so many questions, this board has been invaluable to me since my laptop purchase

Edit: I wanted to add where I'm coming from on this issue. I realize more ram=better. But I am strapped for cash, and seeing as how 1gb stick is more expensive than 2x 512, as well as not being able to resell both 128 sticks as in the above scenario, I want to make sure the 1gb+128mb will actually produce noticable effects over the 512+512.

Oh yeah, I have an acer aspire 3003 w/ a sis mirage 2 graphics chip

I had a question about the worth of upgrading the HD, but it seems going from a 5400 or 4200 to a 7200rpm is mucho worth it. However, could someone explain the different interfaces I'm seeing when browsing newegg? There's ata-5/6/7. Which does mine have? I'm using Everest Home Edition as it was suggested in another thread, but I cant seem to figure out how to find my rpm, or interface.

 

More memory is always usefull- 256 is barely enough to run windows.

You might be able to change the amount of memory used by the graphics card in the BIOS.

 

EDIT: original post edited for clarity, dont need this post anymore.