The old .hack//IMOQ series (Infection, Mutation, Outbreak, and Quarantine) can each be found on sites like Ebay. Though, they have skyrocketed in price. Unfortunately, as Erroneous has said, this is really the only easily available means to play the older games. Though, like others, I hold out hope for a remastered version of them even if they most likely never will do so. If you buy a PS2, I would suggest steering clear of the slim version and get the original model. I've found them to be far more durable. The only downside I've found is they take up more space.
Some soundtracks you can find here and I believe here. Hope this helps. Welcome to the .hack community.