I'm looking to add something else to my kit, somewhere in the $4-500 range and I'm having a hard time choosing between another lens or a flash. I currently have a 18-55 IS, 50-250 IS and 50/1.8 with my T2i. I'd like to get another fast lens or a flash. The lenses I'm looking at are the 28-30 range (either Sigma or Canon) to get a faster lens that is wider than my 50. I'd also like to be able to get better low light photos with my 50-250 if that's possible with a flash but I'm not sure. I've never had/used a big flash so I don't know what to expect. Will it greatly improve the photos I take indoors at a distance of 30-50 feet or do I need to save up for a fast lens? What kind of 'effective distance range' can I expect with a 430 ex ii or 580 ex ii?
I'm going on vacation in a week and a half to the beach so if one or the other would be more useful for good photos at the beach that would be good to know.





