Id say muscle up on a 48/17.
I pushed 48/15 daily for a few months and was out of the saddle quite a bit (loved it!).
I geared down to 48/17 and my acceleration was monstrous, and I learned how to spin.
But yeah. Its up to you. If you can't push 48/17, try 48/18. Going from 15 to 17 was a huge difference for me. So I say just try an 18 tooth cog. Im with Vixtor.
Btw, how do you climb? Do you just exert downward pressure on teh front pedal? cuz I use my back foot to lift AND front foot to push down. It works for me but I dont know if you've tried it yet.
Go with Vixtors idea if you dont wanna muscle up. But I like the idea of muscling up.