If you have to go with a Mares computer then keep your eye on ebay, a seller happy(somethingorother) (NOT ME!) sells lots of Mares gear regularly.
Ive bought a couple of brand new things from them and so have a couple others I know of.
If you check the YD forums you might find a few folk that have had warranty / repair issues with mares computers.
P.S you could also consider getting a different make / model