If you are planning on sticking with a stage 1 then make a low-ball offer and work you way to 350.
I have the v3 and I love the display, 6 gauges all day long but if you plan on installing stage 1 and putting it in the glove box then there's no reason to pony up the extra cash for a bigger screen. I cant remember what year but there are some older wrx's that also require a jumper to install new maps and log so i would double check that your model can do without, or that it will be included.
Welcome to the "i think im gonna be stage 1 for a while" group. Once that mod bug bites it never stops : )
Slow is Smooth > Smooth is Fast