I've tried several different liquors for pouche cafe (I think that's what it's called) and switching the order of high proof and low proof's place improved the visual by a noticable amount.
For example, if you put 10,15,20,23,25,40 % liquor in order, it's easy to mess up a border, there WILL be a border but it's not as horizontal as putting in 10,15,23,20,40,25 in order.
Too bad I use the vodka called "level" pretty damn hard to find, but you can pre-order from duty free and pick up the next time you travel by plane. I gave away my 2 liter bottle of Absolut (almost brand new) for free right after I got level.
And for BRITA + cheap vodka... I'd be very concerned about what happens to filtered water quality after you do that. It's pretty much guaranteed that you'll need to wash the BRITA pitcher, and run through a couple loads of water to clean out any vodka crap (If filtered vodka tastes cleaner, then all the bad stuff is in the filter, right?) that can leak out.
I'll try it out on August 17th, that's when I need to replace my filter so I don't mind ruining an old filter.