Used Alien Invasion is what I did for my "high end", was just under 400. Now they are 500 new. I did a great deal of research and other than being a small company, an ugly gun, and having lame packaging of the marker it's a killer machine, on par with guns twice the price. Requires basically 0 maintenance and still a stacked tube poppit if you are into that sort of thing.
I would also look at a used etek 3 in that price range.
I think the Blitz is best served as a backup or first electro.
Pretty sure the enemy is a mech gun so probably not good for speedball. Also you will want to factor in the price of a decent hopper, Halo Too or Valken V-max ~70 bucks.