Firstly, you can go here to check system requirements for these games you're thinking of.

Secondly, comments on specific games.

1) Dark age of camelot is very PvP focused, from what I hear. That may or may not be your thing. It's also a fairly old game, and past its prime; it has about a fifth the subscribers it once did.

2) Lineage 2 has almost identical system requirements to Aion. If you can't play Aion, you probably can't play L2. Also, Lineage 2 has been criticized pretty heavily for being nothing but a huge grind fest. Keep that in mind.

Lastly, suggestions.

1) Aion. It's supposed to be similar to WoW, while providing some very different play mechanics that provide a unique experience. If you like WoW but just want something new, you'd probably be comfortable with Aion.

2) EVE online. If you're burned out on WoW and want something completely new, EVE will give it to you. It's something of a polarizing game, but the people who like it REALLY like it. On the other hand, it is very corp (guild) centric, so you may find there's not enough single player content for your taste.

3) Champions online. Supposedly a ton of fun, and very easy to play casually. The catch is that the system requirements are a bit higher than for the other games on this list.

4) Wait for Star Wars: The Old Republic. It's still a little ways off, but it's looking amazing in every aspect thus far. Take a break from MMOs and come back when there's a worthy successor to WoW.