Mac for favourites, crown for everything else. Fantastic quality. I personally wouldn't buy mac brushes from ebay, there are whole forums dedicated to counterfeit mac product and brushes, and its very easy to get good looking fakes, if that makes sense! IMO the fakes are a tad scratchy and really shed hairs.
Bobby brown I don't use, but they have a good rep, but again, be very aware of fakes.
I have just got a chanel smudger and its gorgeous.
Estee Lauder brushes aren't a whole lot cheaper than mac, but are at the same high standard, plus they are blue perspex and look really smart, easy to get hold of from boots, debs, house of frazer etc, and of course Estee Lauder are the parent company of mac, so you have guaranteed quality. Hth, Rachael x x