most of your comp is fine.
but the video card it depends.
any card 128m is iffy about lag. JUST becoming outdated for games, but can deal them on low settings no problem.
if you find you lag when near and looking at large amount of bricks, then its video lag, not network.
start by turning down in game resolution little by little till you find it runs better. click off other graphics settings could help to.
you should have no problem playing blockland, but higher graphics settings might give problems sometimes.