My Asus M51Sn has 2 RAM slots which currently have 1x1GB + 1x2GB DDR2-800 SODimm RAM modules installed.

I've found out that 4GB DDR2 SODimm modules do exist, though they are impossible to find in local stores nere here, but I've found them in online stores like these: http://www.pccomponentes.com/g_skill_ddr2_800_pc2_6400_4gb_so_dimm.html

They seem to meet the specification, so can I replace both my current modules with 2x4GB modules, and reach a total of 8GB? Or should I worry about some limit (e.g. 4GB max or 2GB per slot) imposed by the matherboard, chipset or whatever?

(I currently use Ubuntu 12.04 32 bit, so I plan to use the pae kernel, which supposedly supports >4GB ram on a 32bit system; or I may consider switching tu 64bit ubuntu; the question is about hardware limitations, not OS limitations).