The best mixed seed I've ever been able to find are the President's Choice wild bird seed and AllSeason wild bird seed -- and while both have the highest count of sunflower seeds and peanuts I've found, they still have a fair bit of "filler" seed -- millet.
my local co-op has begun a bulk seed bar which lets you pick between a variety of seed -- black striped sunflower, black oil sunflower, safflower, millet, hulled sunflower and both shelled and in shell peanut. I switched to that for a bit but the problem is you have to bag each separately b/c they're priced differently -- so you're using many plastic bags -- and then you have to mix at home. Typically I would buy the black oil and striped sunflower with shelled peanuts.
I've noticed that black oil sunflower seed are relatively cheap in a huge bag so today I went with it. No striped sunflower....no shelled peanuts...no safflower (which frankly I didn't find particularly popular except with cardinals but they also like the sunflower seeds so....)....I have a big bag of in shell peanuts for the red squirrels and jays that I"ll scatter on the ground...we'll see how this turns out. Anyone else go with one type of seed?
Oh....and I'll be testing out a new feeder I "won" on silent auction at a recent Ducks Unlimited fundraising dinner. It's a platform feeder made to look like a drake mallard -- it's Amish made out of old barn board -- a Pine Bush Home and Garden product. It came with a mark's choice bag of premium wild bird seed...which is mostly millet....