Personally, I can tell a night and day difference between a short ram and a CAI. You've already got the Injen Short Ram, so get the Cold Air Extension from Injen at
www.overboost.com. I think I paid something like $65 shipped, maybe a bit less for the CAE. I found the injen short ram on Ebay for about $70.
You won't have to worry about water unless you actually drive THRU puddles. I've driven behind lots of cars in rush hour while it's raining very hard and everyone is splashing water up, and there is NO water entering the engine, even under full boost. Not to mention my intake temps AFTER the JRSC (on the manifold) are at least 70 * cooler than the top of the engine itself, AT LEAST and that's even during the hottest day of summer, even after a LOT of continuous boosting. Even a hondata gasket would help, and I only have a stock one. And yes, if you put cold air through the JRSC, it will automatically heat it up from compressing it, but not NEARLY as much as you'd think. If the ambient temp outside is 50*, and I'm boosting a LOT, I can still feel coldness on the whole intake piping tract, into the s-pipe it gets a bit warmer, and aft of the blower (on the manifold), it's warmer still, but you can put your hand on it and not burn yourself at all. It's only luke warm to the touch.
For what it's worth, I don't believe that the JRSC has much more trouble pulling cold air from the bumper than it does using a short ram... it's only about 2-3 feet longer. Also, it is my assumption that it is easier to start going from a stop with a CAI than it is from a custom cold air box, simply because the length of sucking through piping is less with a CAI than it is with a custom cold air box. A custom cold air box will add another 3-5 feet over and above a CAI.