Lack of support for Dell 8700

I purchased my Dell 8700 in Jun 2014.  As of Dec 2015 I have replaced my 3rd motherboard.  By the end of the first yea. warranty, I had replaced the motherboard twice.  I expressed my concern for the machine's reliability, but was told I needed to purchase an extended warranty in order to assure against future problems, which I did.  Now, 7 months later, I have again had to replaced the motherboard.  Definitely something wrong here!  After several discussions with tech support, including with Tier 2 stateside, the only solution offered is, I need to buy additional extended warranties (at $200+/yr.).  Apparently Dell doesn't stand by their machines!  Very disappointed!!  I'll be scrapping this machine before I have further issues and will never purchase a Dell product again.