Nelson tune + CAI on 2005 5.3?

Hi, I am new here and have been searching around for a few hours this morning. I havent found exactly what I am looking for but close! I really have enjoyed looking over this site the last few days.

My truck is a totally stock 5.3 with auto trans. I'd like to add some power but keep low end power the same for towing. Ive seen posted a dyno chart where a cold air intake added 15whp. Is that possible? That sounds great for the cost. If I took the truck to Nelson for a live tune, then that might add 30-35whp? Is it possibe to get near 50whp for only $600 or am I missing something?

I was considering doing a small cam like the Comp Cams 212/218 @ 050 but am not sure its worth the expense if I can get a real 50whp with a CAI and tune! Would a small cam like that require different springs or could I use stock springs/retainers/pushrods?

Thanks for your advice!!
Hez