What should I really expect?

With those specs you should be OK s DAI is not that demanding a game specs wise but if you enjoyed Origins then you likely will enjoy DAI as it is probably closer to DAO than DA2 in terms of the kind of things you'll be doing. As like with Origins you're dealing with a worldwide threat. The main difference between DAI and the earlier games is that DAI is a bit more action focused in terms of the combat so that might take some time to get used to. For me personally it's my favourite of the 3 games and deserved it's game of the year status that it got but everyone has their own opinion. As with the DLC's I have all of them and yes they're thoroughly enjoyable. I would advise though if you play them play them with a higher levelled character at least close to or higher than level 20 as the combat is harder than in the normal game levels

I'm sorry, I'm just here to say that Alistair approves 100% of your nickname.

carry on topic.

My memory might be a bit fuzzy, but if you want to play all the DLC, stay away from PS3 or any other archeotech hardware (like XBox360). Not all DLC was published for those platforms, the later ones are only available on current generation consoles and PC.

If you liked the DAI vanilla game, give the additional story DLC a shot! Some people argue that the final one, Trespasser, contains the actual ending, while others feel that it messed up their protagonist's story.

Avoid the armor DLC, I forgot what its name was, but the quality is sub par.

Nevermind the DLCS. DAI looks horrible in the PS3.