As you said, if you keep Sturridge fit you've got a pretty nice team on your hands. Then again Firmino is quite versatile and could do a job, Ings is decent but it's best for the team if you've got a system with Sturridge at the attacking pivot as the cover strikers you have are; shall we say... less capable.
Sturridge
Coutinho------------Firmino
Henderson Milner
Can/Lucas
It's true the top 4 teams are strengthening but if you beat the teams you need to like you did in that 13 games unbeaten streak was it? And do your part then there's nothing to suggest that you can't make a respectable challenge for the Top 4.