Xanafir.3471

well I found a webpage that told me to alter steam's guild wars 2 launch options to -provider Portal. which allows me to use my login account for when i first bought it before steam every got the game. so I was just wondering if I had to buy the steam xpac or the site's xpac. and if by doing this could I still play with my friends on steam

Okay here's the deal, I have managed to get steam to let me log into guildwars 2 through my orginal game account and not the one produced by steam. so here is my question. If I get the xpacs on the store for 50, would I still be able to use them on steam? or would I have to download/install the game client?