Pretty good squad mate but I'm sure you can improve on it. But it all depends whether you want to hold on to most of the original Liverpool players or you couldnt be bothered either way.
For a start, your defence could do with some bolstering. Carragher is too old as you've mentioned. So either stick him in the reserves or sell him so he can continue his career elsewhere (no sentiments please!!

). You can easily find better CB's than Agger & Skrtel. Pique is good. Zapata, Djourou, Sakho, Pepe, Garay, Breno, Criscito are just a few. I'd suggest getting atleast one, if not two to shore up your D. You can also do better at RB than Ryan Taylor & Arbeloa! De Silvestri, Lahm, Sagna, Rafinha, Behrami are some potential targets.
I'd look at a better keeper than Reina too. He's definitely very good but not the best around. Akinfeev & Ustari are the obvious choices. Ochoa, Lloris are 2 very worthy contenders too. Bouzanis becomes brilliant so I'd definitely keep him.
The midfield is your best area. Looks solid all round. 2 great DM's, great CM, good wingers. Dont think you need to improve much here unless you're planning on going for the big guys like Messi, Ronaldo, Silva etc.
I'm surprised you've managed to get by with only 2 strikers (Babel is better as a winger
imo). In that, 1 is pretty poor. Need to invest heavily here I'd say. Atleast 2 more are a must. 1 great one (much like what you're trying to get - Aguero) and 1 good backup (better than Voronin). There are so many out there. Have a look at Fred, Briand, Balotelli (becomes class in a few years), Saivet, Vela, Cavani, Bendtner to name only a few. Just get whoever you fancy really.