Name Brand Blubs vs (other), Where do you buy your bulbs from?

I have an old 1000W HPS system, & I think the bulb needs to be replaced (even though it works).

I'm wondering, for those of you who grow with HPS lighting systems, when you buy bulbs (individually),
Do you try and buy "name brand" bulbs? Do you feel like different bulbs, although same wattage, feel any different?

Also, where do you buy your bulbs at? Grow shops? eBay? Online shops?