I think you underestimate the scope of opening theory and overestimate the efficiency of sticking to a few "pet lines".
As already mentioned by bof, playing ..c5 against 1 d4 has little to nothing to do with the "Sicilian Defense". White very specifially has to continue with e4 in the second or third move (after 2 c3/Nf3) to transpose into the Sicilian. Any other moves and you are in a completely different opening with very own motives and ideas. Actually, there is no such thing as "the" Sicilian either: White has no less than 4 common alternatives for his second move alone (Nf3, Nc3, c3, d4) that lead to very different positions.. and it's not going to get better from that point on regarding the size of the move tree. Telling us that you play "the Sicilian Defense" is equally vague, as there are many different systems Black can use (based on g6, e6 or e5, mainly).
Trying to only play lines that are similar to each other will lead into a dead end in the long run (even if it might be successful for now). It's an illusion, especially when playing Black: No matter what you do, your opponent always has the choice to disturb your plan by playing a line you don't like (e.g. an early Bf4/Bf5/Bg4/Bg5 can be a real pain if you try to play Stonewall Attack/Dutch). Most openings offer the possibility for both players to choose either really sharp or really quiet continuations, and you have to adapt to the choices of your opponent. Because the higher your rating, the better your opponents will get in adapting to you.
The 1 d4 c5 variation illustrates this point pretty well: Because you don't have the full picture yet and only tried to apply the (Sicilian) schemata known to you, the variation gave you a lot of trouble. kmartin on the other hand applied a common motive from the Queen's Gambit (variations of this can be found in many other openings, e.g. the French Defense) to prove that you can take back that pawn with tempo (or trap the opponent if he's too greedy) and have a comfortable game (after 4 Nf3 d6, your position isn't that much away from a common Sicilian one after all, hooray!).
So, my advice would be that instead of asking us and thus limiting your attention to only one or maybe a couple of defenses with the same patterns you already know, give ALL of them (and the White openings, too, of course) an honest try yourself*. Then you can make that choice on your own. And even if you end up choosing the Stonewall Attack and Dutch Defense as your favorites anyways, having looked into the others and thus broadening your view will pay off, believe me.
And no, time consumption is not an excuse. Whoever devotes the time to ponder the question of his opening choice enough to consider asking it on stackexchange also has 10 minutes to look up the main lines of some opening before he starts playing. The actual work is nicely hidden in that playing.. which by itself should be considered a pleasure, not a chore, right? :)
*It's okay to look up variations as long as you don't overdo it. There are a lot of purists around that claim that noone below 2000 elo or some other number should be learning any opening theory at all, but I disagree with that. You don't have to reinvent the wheel. You should however put a serious effort into trying to understand how cars work and what the differences between a Mini and a SUV are before you settle to buy one. ;)
