Does memory stick frequency difference matter?

No issues -- RAM always downclocks to the slowest stick installed. No matter what speed you put in, as long as DDR2-400 is installed all other RAM will run at DDR2-400 too. In this case your 800MHz ram would run at 400MHz.

If you are using DDR2 400 check your computer motherboard specs on the manufacturer's website and make sure it can handle the extra RAM. Older boards sometimes were capped at 2GB.

in my view i do no longer see lots of an progression in overall performance after having upgraded from 1333mhz ram however the version is small. In asserting that quicker ram will make a difference how ever small it is going to likely be greater efficient and you may see a fps progression for gaming,a million-3fps max optimistically. yet while i've got been you i might defiantly pay that extra funds for the Kingston ram simply by fact they seem to be a properly well-known and extremely warm organisation, i'm kinda irritating approximately that variety much less ram, it must be fairly poor high quality and can fail. on a area no longer that Kingston hyper X ram seems super a buddy of mine has it in his rig.