Wow - a lot of bad advice.
First: Between AMD and Intel, you will NOT see a difference in reliability regarding the CPU and Chipsets alone. I think it odd that you ask for differences in reliability, and then mention MSI motherboards. MSI is known for middle of the road boards. Go with Asus, EVGA, or higher end Gigabyte motherboards for rock solid stability. I prefer EVGA myself. Don't bother with Extreme editiion CPU's. Get the 'K' series just below it, and overclock as needed.
As for ram, go with GSkill, Crucial, or Corsair. ALL THREE are going to be reliable. Pick the cheapest set with the timings, and clock rate you are looking for.
For a power supply - DO NOT cheap out on the power supply. Go with Corsair TX/AX/HX series, Seasonic, Antec HCP/HCG series, or PC Power and Cooling Silencer series. Those are quality units with stable power.
As for the Alienware debate. This is easy to settle. Years ago, Alienware was considerably overpriced. They make premium machines and sell them at a premium price. You won't find them skimping on the power, or the motherboards, hard drives, etc. Lately, their prices have fallen more inline with their premium GAMING competitors. Expect them to charge more than ibuypower, but expect a better product with better service. I avoided Alienware for MANY years due to the "overpriced" mentality. Then I met several people who spoke highly of them, and decided to try one for myself. I quickly found out their prices are justified with well designed gaming machines that easily handle what is asked of them.You will find many polarized opinions of their machines. Understand that EVERY manufacturer has a certain failure rate. Anecdotal evidence doesn't count for much. So don't take it for much. However, the things that do count, are the places where a company does or does not skimp out. Like a terrific metal chassis, and aluminum body, a quality IPS display, and top tier hard drives (the AW 14 shipped with a WD Black edition drive!). These things speak of a company trying to do their best to release a quality product. I found the same with Lenovo: Top quality Chasis, with wide color display, and top tier hard drives.
Would I recommend an Alienware desktop? NO. I will still hold to the statement that you can build a higher quality machine at a lower price on your own. Would I recommend an Alienware laptop? MAYBE. It depends on what you need it for. For gaming? YES. For general use, or business use, NO. Get a Lenovo for those.
In short, build this machine, but do it right. Intel still has the faster high end, and I would suggest it.