At that bodyfat, you don't need to worry about cutting as an urgent matter.
It's not a bad bodyfat for gaining some muscle either.
I'd say you're in a better position to gain some lbs now than you was at the start. You've got stronger so it's going to get harder to get even stronger.
You can do it though and I think with all of the advice outlined above you can still do it with SS. I'd give it another month at least trying the advice you've got and if you still see no good progress and you have diet in check then maybe consider moving on to something else.
I would say if it comes to it or when it comes to it go on to bill stars 5x5 programme.
Rippetoe has you doing 3 work sets and if you're doing 4/5 work sets on bills programme then you are set to make some new gains. You should consider madcow as an alternative as well.
You can find out that stuff on the starting strength wiki or just googling bill starrs 5x5 wiki. It's a little more volume and it's not so drastic of a change that your body wont adapt in a beneficial way in my opinion. I'm doing starting strength right now and that's what I plan on doing mid 2011.
I know this next bit of advice is probably a stretch too forward thinking but if you can do these sort of programmes for two years stretching out your gains as long as possible by tweaking the programme here and there when you need to, then you will be set for a proper bodybuilding split at the end of it.