thats a good thing in snow.. understeer is basically the last thing you want in snow. and anyway, the ix handles extremely neutral, maybe a slight tendancy to oversteer, which is perfect for a snow car. ive driven a shit ton of different cars in snow. 2 different sti's, a wrx, a b5 a4 and s4, an ix, an s60r and more. ive driven the the sti and ix back to back, and the ix absolutely destroyed it. it was just soft enough to pitch the weight around very easliy, and its nearly perfectly balanced in the snow, you can get it to do whatever you want. the sti just pushed like crazy nomatter what you did, you could try flicking the crap out of it and if you were lucky you would be able to enter a corner with decent rotation. but 9 times out of 10 you plow from turn in to apex, then have to break the rear loose with power and "drift" out.
anyway out of all those cars, the audi's definitely had the best grip, but the ix was by far the best balanced. but it has a much better ABS system, higher ride height, much tougher, 10 times more reliable, and just overall more fun, so the ix gets my vote :)
and no its extremely easy to find one thats in good condition, e30's especially ix's are usually enthusiast owned, yeah you have to be careful and have a couple choices. but its very easy to find a well taken care of e30.
and i dunno what your talking about with it being small, its perfectly sized, the front seats are awesome, plenty of room in the front, and the rears even on a 2 door were plenty roomy for a compact car, better than most anything else you can get for 3k. we took a 30 hour road trip in my friends e30 with 3 people, and like 250-300 lbs of luggage. not the most ideal car for that, but it was fine. and we were able to cruiser at over 100 pretty easy and cruise around 75-80 at 10,000 feet up hills, and its stock.
if i had 30,000 dollars to spend on any snow car, id still choose an ix, because i honestly cant think of anything that would perform better.