In my experience Praise and Worship music crosses many musical boundaries so my suggestion is to look at something that has a broad range of sounds as my guess is that your requirements will change overtime.
If you already have Sonar Platinum then I would check out what is on offer from Dimension Pro and Rapture both have some good pads across a variety of styles as does Z3TA although this tends to really excel at other uses. There are a lot of presets to work but if you combine searching with patience you should find some sounds to get you started.
Worth looking at the AAS bundle as well Analog Session specifically.
If you want to go outside of what comes with Sonar then the Korg Collection includes the WaveStation which is capable of some amazing evolving pads along with a number of other classics. SampleTank is a good source of all round sounds and Syntronik is fantastic in my opinion and IK Multimedia offer a free version of both of these to help you assess.
There are plenty of other options too depending on budget with some pretty good free stuff.
Don't forget hat some of the best sounds are layers with some effects added and most sounds will sound better if you adjust/personalise them.