Hello all, i'm thinking of buying a new 15 in MBP with Retina. Should I get the upgrades from Apple stocks? Processor, Storage and Memories? or should I just upgrade later and get it from third parties for the upgrades? I'm just a low end user but I don't mind having the bells and whistles. Please advise. Thanks.
As is the case with most laptops, the processor is not upgradeable, so it really depends on how long you want to keep your computer and what you plan on using it with. I'm using an almost 3-year-old 2.5GHz i5 iMac at work and it's plenty fast for everything I do (virtual machines, some web/media content), but my personal machine is a 2.9GHz i7 (mid-2012 MBP) and I think I went a bit overkill on that (it certainly is faster than the iMac for some tasks, but I can probably survive waiting an extra second or two).
For memory, you're also stuck with whatever you get originally on the Retina MacBook Pros and the MacBook Airs. Apple's prices aren't bad, and it's really up to you if you want to spend the money to get the 16GB version. Whenever we do a built-to-order one for work, we usually opt for 8GB so there's a bit of "breathing room".
As far as storage, that is a replaceable component, but not necessarily as easy as replacing a 2.5" hard drive or a 2.5" SSD. In that case, buy what you can afford, but this is one area you can skimp early on.