Which configuration of iMac 27" ? Fusion drive or not ? RAM upgrade ?

Question

I'd love to get a new 27" iMac for my Mother, but cannot decide if the higher i7 processor (3.5) is worth the price, and cannot decide if the 3TB "Fusion" drive is worth the extra $350. 
The retail Apple stores stock the i7 only with the 3TB Fusion drive, the better graphics card, and stock 8GB of RAM, but one can configure the machine if ordering on-line via the link below.   Her husband will reimburse me or it will be a gift.  Money is not the issue.... just whether or not the money is worth spending.
One last thing:  The apple store rep said that the "Geniuses" have to do the RAM upgrade, say from 8GB to 32GB because the 21" unit has to be opened.  So the consumer doing the RAM upgrade will void the warranty. Yet I see website indicating that the 21" has a nice convenient door to open and the RAM is user-upgradable without voiding the warranty.  Which is true ?
Apple wants to charge $600 (parts and labor) for the RAM upgrade to 32GB.   But Crucial has 32MB of this RAM for under $300 with a lifetime warranty.  Is there a reason to use the RAM from Apple ?
LINK: http://store.apple.com/us/buy-mac/imac?product=ME089LL/A&step=config

Answer 1

1. 27" iMac with 3.4Ghz i7 and NVIDIA GeForce GT 775M with 2GB video memory is just $200 more than 27" iMac with 3.2Ghz i5 and NVIDIA GeForce GT 755M with 1GB video memory. How much is her time worth per hour? If it's for business use, it pays for itself quickly. Same opinion for the 'build-to-order' upgrades in speed and video available on the 27" i7.
2. Fusion drive is a hybrid combining 128GB SSD with either a 1TB or 3TB rotating platter hard drive.
Analysis and review of Fusion drive in a 2012 iMac: http://www.anandtech.com/show/6679/a-month-with-apples-fusion-drive
Conclusions and performance are on pages 5 and 6 of the review.
3. 27" iMac RAM is "user-replacable", quoting from the 2013 'Important Product Information' addendum to the manual:
"Do Not Make Repairs Yourself
Your iMac doesn’t have any user-serviceable parts, except for memory, which is user-replaceable in 27-inch models only. Do not attempt to open your iMac. If your iMac needs service, contact an Apple Authorized Service Provider or Apple for service.
If you open your iMac or install items other than memory in 27-inch models, you risk damaging your equipment. Such damage isn’t covered by the limited warranty on your iMac."
quoted from http://manuals.info.apple.com/MANUALS/1000/MA1662/en_US/imac_late2013_ipig.pdf
OWC video of the 27" RAM upgrade installation: http://eshop.macsales.com/installvideos/imac_27inch_late_2012_mem_m/
4. If it's for business, go for the i7 and the video upgrade.
5. I'd do the upgrade myself, purchasing from a reliable vendor of Apple RAM such as crucial.com or macsales.com. I have no experience with the other vendor you mentioned, RAMfinder.com. Factory-installed RAM offers the pricey convenience of having a machine configured by you online and shipped directly to your mother in a few days with no one else needing to be involved.  I'd avoid any Apple salesperson who apparently doesn't know the 27" iMac product well enough to give you the truth about user-installable RAM upgrades. OWC (macsales.com) will purchase system-pull original RAM allowing you to recoup a small portion of the cost of the upgrade, though nothing close to the resale price of the RAM.
Message was edited by: kostby